| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
-butyrolactones
1 Mikrobiologie/Biotechnologie, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
2 Max-Planck-Institut für Entwicklungsbiologie, Spemannstr. 35, 72076 Tübingen, Germany
3 Leibniz Institute for Natural Product Research and Infection Biology, HKI, Beutenbergstr. 11a, 07745 Jena, Germany
Correspondence
Eriko Takano
e.takano{at}rug.nl
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMETHODSRESULTSDISCUSSIONNOTE ADDED IN PROOFREFERENCES |
|---|
-Butyrolactones play an important role in the regulation of antibiotic production and differentiation in Streptomyces. However the biosynthetic pathway for these small molecules has not yet been determined, and in vitro synthesis has not been reported. The function of the AfsA family of proteins, originally proposed to catalyse -butyrolactone synthesis, has been in debate. To clarify the function of the AfsA family, and to understand the synthesis of the -butyrolactones, we performed in silico analysis of this protein family. AfsA proteins consist of two divergent domains, each of which has similarity to the fatty acid synthesis enzymes FabA and FabZ. The two predicted active sites in ScbA, which is the AfsA orthologue found in Streptomyces coelicolor, were mutated, and -butyrolactone biosynthesis was abolished in all four constructed mutants, strongly suggesting that ScbA has enzymic activity.
Full details of the construction of ScbA mutants and further MS data are available as supplementary data with the online version of this paper.
Present address: Department of Microbial Physiology, GBB, University of Groningen, Kerklaan 30, 9751NN, Haren, The Netherlands.
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONNOTE ADDED IN PROOFREFERENCES |
|---|
; Vendeville et al., 2005; Venturi, 2006). -Butyrolactones are produced by the Gram-positive soil-dwelling bacteria Streptomyces, and they were among the first signalling molecules to be identified (Khokhlov et al., 1967). The first and the most well-characterized -butyrolactone is A-factor from Streptomyces griseus, and it is required in nanomolar concentrations for antibiotic (streptomycin) production and sporulation. Today, several -butyrolactones are known, including the Streptomyces coelicolor butyrolactones (SCBs), which regulate actinorhodin and undecylprodigiosin, and the recently identified polyketide synthase biosynthesis cluster Cpk in S. coelicolor (see Takano, 2006, for a review; Yamada, 1999). The first -butyrolactone biosynthesis analysis was that of virginiae butanolides (VBs) isolated from Streptomyces virginiae; this synthesis is thought to involve a condensation of the glycerol derivative dihydroxyacetone and 7-methyl-3-oxo-octanoyl CoA to form a 7-methyl-3-oxo-octanoic acid. In the presence of NADH, this is then converted into 6-dehydroVB A, and further to VB A in the presence of NADPH (Sakuda et al., 1990, 1992, 1993). However, in vitro synthesis proving this biosynthesis pathway has not been reported. Recently, Shikura et al. (2002) identified a stereospecific reductase essential for the last step in VB production.
A putative A-factor biosynthetic gene, afsA, has been cloned from S. griseus (Horinouchi et al., 1985), and a number of homologues of AfsA have subsequently been identified from several streptomycetes (see Takano, 2006, for a review). However, in vitro A-factor synthesis has not yet been demonstrated, and little is known about how the synthesis is controlled. Cloning of afsA on a multi-copy plasmid leads to precocious production of streptomycin in S. griseus, and synthesis of A-factor in several Streptomyces species that normally do not produce it (Horinouchi et al., 1985). Expression of afsA in Escherichia coli also results in production of biologically active -butyrolactones; this expression is reduced in the presence of cerulenin, a fatty acid synthesis inhibitor (Ando et al., 1997). From these results, and those obtained by Sakuda et al. (1990, 1992) outlined above, it has been concluded that AfsA on its own can produce A-factor from a glycerol derivative, and an 
-keto acid derived from fatty acid biosynthesis.
A contrasting view arose from studies of the gene barX. barX is an afsA homologue from S. virginiae that is located adjacent to barA, which encodes the VB-binding protein. A barX-deletion mutant produces less virginiamycin and VBs, but the addition of VBs to the mutant does not restore virginiamycin production (Kawachi et al., 2000), in contrast to the situation reported for the afsA mutant in S. griseus (Hara & Beppu, 1982). Furthermore, BarX enhances the stability of the interaction between BarA and its cognate barB (barA homologue) promoter by a protein–protein interaction that leads to repression of barB expression. Thus, the authors conclude that BarX does not possess enzymic activity analogous to AfsA, but that it may be involved in the regulation of VB synthesis.
scbA is the afsA homologue in S. coelicolor, which is genetically the most well-characterized streptomycete, and has a completely sequenced genome. scbA is located divergently from the -butyrolactone-binding protein determinant scbR (Takano et al., 2001), thus exhibiting the same gene organization as S. virginiae (see Takano, 2006, for a review). A deletion mutant of scbA does not produce any -butyrolactones with antibiotic stimulatory activity, and expression of scbA is absent in both scbA- and scbR-deletion mutants. While the expression of scbR is induced by addition of SCB1, a -butyrolactone, to the scbA mutant, scbA transcription is not inducible under the same conditions (Takano et al., 2001). Thus, some direct role for ScbA in transcriptional activation of its own gene appears probable, suggesting a possible regulatory function for ScbA. Production of SCBs is detected at transition to stationary phase, and this also coincides with the transcription of scbA (Takano et al., 2001).
To clarify these conflicting results, and to understand the function of ScbA and the other members of the AfsA family, we undertook an in silico analysis of the protein sequences. From these analyses, a number of conserved residues that are likely to participate in an enzymic function of ScbA were identified. Point mutations in these positions were created, and the resulting S. coelicolor strains were tested for the ability to produce -butyrolactones with antibiotic stimulatory activity. All the point mutations tested resulted in loss of antibiotic stimulatory function, indicating that ScbA is indeed an enzyme involved in -butyrolactone synthesis, and that it is structurally and functionally related to bacterial fatty acid synthesis enzymes.
|
METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONNOTE ADDED IN PROOFREFERENCES |
|---|
. Streptomyces strains were manipulated as described by Kieser et al. (2000). E. coli was grown and transformed according to Sambrook et al. (1989). SMM (Takano et al., 2001) was used for RNA isolation, isolation of -butyrolactones, and antibiotic production determination. SMMS agar (Takano et al., 2001) was used for -butyrolactone bioassays. MS agar (Kieser et al., 2000) was used to make spore suspensions, and for plating out conjugations with E. coli ET12567 containing the RP4-derivative pUZ8002 (Flett et al., 1997). R2 (Kieser et al., 2000) and R2YE (Kieser et al., 2000) were used to observe morphological differentiation and antibiotic production of mutants.
|
. Amplification of DNA by PCR was done with Taq polymerase or ProofStart polymerase (Qiagen). E. coli colony PCR was carried out by mixing a small amount of cells picked from a single colony directly into the PCR reaction pre-mixture. DNA was sequenced by MWG.
|
. Streptomyces genomic DNA was isolated according to Leblond et al. (1996). RNA was isolated as described by Strauch et al. (1991).
Construction of ScbA mutants.
The conserved glutamates E78 and E240 of ScbA were mutated to alanine, and the conserved arginine R243 was mutated to lysine by site-directed mutagenesis using SLIM (Chiu et al., 2004), to yield pTE106, pTE108, pTE104 and pTE110. For full details of the construction of ScbA mutants, see the supplementary data available with the online version of this paper.
Introduction of the mutation into Streptomyces.
pTE104, pTE106, pTE108 and pTE110 were introduced into the methylation-deficient E. coli strain ET12567 containing the RP4-derivative pUZ8002 (Paget et al., 1999), and transferred to S. coelicolor M751 by conjugation (Flett et al., 1997); single-crossover exconjugants were selected on MS containing apramycin and nalidixic acid to obtain transconjugants M751 : : pTE104, M751 : : pTE106, M751 : : pTE108 and M751 : : pTE110, respectively. The genomic DNA of each strain was isolated, and plasmid integration was confirmed by PCR with primers JGatt B1-fwd and JGatt Pint-rev (Table 2
), which gave an amplified product of 0.8 kb, corresponding to the inserted region (data not shown).
RT-PCR.
RT-PCR was conducted using RNA isolated from M751 : : pSET152 (negative control: mutant complemented with vector), M751 : : pIJ6147 (positive control: mutant complemented with wt scbA), M751 : : pTE104, M751 : : pTE106, M751 : : pTE108 and M751 : : pTE110 grown in SMM liquid medium for 24 h (see Fig. 3a). A 2 µg quantity of RNA was used to synthesize the cDNA, and 27 ng of this cDNA was used as the template for the PCR reaction, as previously reported, using primers for scbA, hrdB, redQ, redD, actII-ORF4, cpkO, cpkE and actIII, except that the PCR conditions in the present study were 96 °C for 5 min, then 30 cycles of 96 °C for 40 s, 58 °C for 40 s, 72 °C for 40 s, and extension at 72 °C for 7 min (Takano et al., 2005).
|
-butyrolactone formation.
Other methods.
-Butyrolactones were isolated and the bioassay was conducted as described previously by Takano et al. (2001). M145 : : pSET152, M751 : : pSET152, M751 : : pIJ6147, M751 : : pTE104, M751 : : pTE106, M751 : : pTE108 and M751 : : pTE110 were grown in SMM liquid or on SMMS solid medium, and ethyl acetate extracts were made from stationary-phase culture supernatants at OD450 1.2 (the last time point in Fig. 3a). Equal amounts of the supernatant extracts were spotted onto confluent lawns of the indicator M145. After 48 h incubation, the antibiotic stimulatory activity was determined (see Fig. 3b). Antibiotic production assay was conducted using 1 ml samples of cells grown in 50 ml SMM, as described by Strauch et al. (1991).
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONNOTE ADDED IN PROOFREFERENCES |
|---|
). These repeats show no similarity to any other proteins in the databases when using standard BLAST or PSI-BLAST searches (Altschul et al., 1997). A sequence search of all proteins with known structure using the advanced remote homology detection tool HHpred, which is based on pairwise comparison of hidden Markov models (Söding et al., 2005), revealed that ScbA consists of two domains homologous to the superfamily of thioesterase/thiol ester dehydrase-isomerases defined in the SCOP database (Murzin et al., 1995). Each of these domains contains the described AfsA repeat as their most conserved part. Two members of the thioesterase/thiol ester dehydrase-isomerase superfamily, namely FabA (
-hydroxydecanoyl thiol ester dehydrase) and FabZ [(3R)-hydroxymyristoyl ACP dehydrase], have several conserved active site positions that also appear in both domains of ScbA (see below). Moreover, FabA and FabZ are functional as homodimers whose two active sites are located at the dimer interface (Leesong et al., 1996; Kostrewa et al., 2005). This strongly suggests a similar spatial arrangement of the two domains in ScbA. Although the overall sequence similarity of ScbA to FabA and FabZ is weak (15 and 13 % amino acid identity, respectively), the similarity in the region around the FabA/FabZ active site is pronounced, and, in particular, the hydrophobicity pattern is well conserved (Fig. 1).
|
-helix of one subunit, and a loop that is N-terminal to the equivalent helix of the other subunit. The residues involved in catalysis are a conserved aspartate/glutamate located in the helix, and a conserved histidine present in the loop region that forms the catalytic diad. A conserved glutamine forms a hydrogen bond with the carboxyl side chain of the conserved glutamate/aspartate residue, and stabilizes its position (Leesong et al., 1996; Kimber et al., 2004; Kostrewa et al., 2005). In ScbA, the glutamates (E78 and E240) and glutamines (Q82 and Q244) are perfectly conserved in both domains, while the histidine residue is present only in the C-terminal domain. In other homologues, the C-terminal histidine is replaced by an arginine (H226R) (Fig. 1). This may be related to, or the functional difference between ScbA and FabA/FabZ may be due to, the arginine residue that is well conserved in both domains of ScbA (R81, R243), and that is situated just before the conserved glutamine, but not present in FabA or FabZ.
Mutagenesis of the predicted active-site residues in ScbA: E78, E240 and R243
To test the prediction that these homologous amino acids are involved in forming the active site of ScbA, the conserved E78 and E240 were mutated to alanine, and the conserved R243 was mutated to lysine, in the AfsA repeat domains. E78 and E240 were mutated to alanine separately to yield pTE106 (E78A) and pTE108 (E240A), respectively, and together to yield pTE104 (EA). The conserved R243 was mutated to yield pTE110 (R243K) (Methods; Figs 1 and 2). These constructs were then introduced into the scbA deletion mutant M751 by conjugation, to give strains M751 : : pTE104, M751 : : pTE106, M751 : : pTE108 and M751 : : pTE110. The original promoter was retained in all constructs.
|
-butyrolactones, even though the mutated genes were expressed-butyrolactone was tested by bioassay, looking for the ability of ethyl acetate extracts isolated from stationary-phase cultures of the strains to induce pigmented antibiotic production in the indicator strain M145 (as detailed in Methods). The results are presented in Fig. 3(b). As reported previously, an extract from the positive control strain M751 : : pIJ6147 stimulated pigmentation; however, it needed extracts that were twofold more concentrated than that of M145 : : pSET152. Extracts from M751 : : pTE104, M751 : : pTE106, M751 : : pTE108 and M751 : : pTE110 showed no antibiotic stimulatory activity, even when using a twofold excess of supernatant extract compared with the positive control (Fig. 3b). This result indicates that the amino acid replacements (E78A, E240A and R243K) in these two putative active sites leads to an inability to produce active -butyrolactones.
These results were corroborated by analyses of the metabolic profiles by HPLC-MS, using a synthetic reference of SCB1. As shown in Fig. 3(c), only M145 : : pSET152 and M751 : : pIJ6147 were capable of producing SCB1, while no related -butyrolactones were detected in the mutants. MS revealed the characteristic fragmentation that is initiated with the loss of two molecules of water (see supplementary Figs S1 and S2 available with the online version of this paper).
To exclude any possibility that the mutated scbA constructs were not being correctly expressed, RT-PCR was conducted, as described in Methods. The expression of hrdB encoding the major sigma factor for S. coelicolor was readily detected in all samples (Fig. 3d), while the scbA transcript was detected in all the samples except M751 : : pSET152, which is the scbA deletion mutant with an integrated vector only (Fig. 3d). No amplified products were detected using RNA as a template, which suggests that there was no DNA contamination of the RNA samples (data not shown). This suggests that scbA was expressed in the mutants, and that the mutations, and not the loss of transcription, led to the loss of bioactive -butyrolactone production.
To assess the effect of the mutations on growth and antibiotic production, M751 : : pTE104, M751 : : pTE106, M751 : : pTE108 and M751 : : pTE110 were grown on several different solid media (R2, SMMS, R2YE and MS) in triplicate, but they showed only slight differences compared with wt : : pSET152 or M751 : : pSET152 (data not shown; see Discussion). The mutants were also grown on SMM liquid media at 30 °C in triplicate, and, after 18 h incubation, samples were taken at four time points (every 2 h) and after 34 h at OD450. The level of antibiotic production of undecylprodigiosin and actinorhodin was different at each time point, and no conclusion could be made from these results (data not shown). RT-PCR using the undecylprodigiosin-pathway-specific activator RedD, and a representative biosynthesis gene, redQ, the actinorhodin-pathway-specific activator actII-ORF4, and a representative biosynthesis gene, actIII, the Cpk pathway-specific activator CpkO, and a representative biosynthesis gene, cpkE, was conducted in triplicate to determine the effect of the mutation on the expression of these genes. The expression levels of the three biosynthesis genes were similar in all the strains tested (Fig. 3d). The three activators showed varied expression levels (data not shown), which may correspond to the growth phase in which the RNA was isolated (see Discussion).
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONNOTE ADDED IN PROOFREFERENCES |
|---|
-butyrolactone synthesis has been under considerable debate for the last decade. Moreover, the exact biosynthetic pathway for the -butyrolactones is unknown, despite their importance in the regulation of antibiotic production. Our results point strongly to a role for ScbA in the biosynthesis of SCB1.
Standard BLAST analysis of the AfsA family of proteins has not revealed any similarity to other proteins in the database since the sequencing of AfsA in 1985. By using the novel software HHpred (Söding et al., 2005), we were able to determine, for what we believe is the first time, that ScbA has active sites similar to fatty acid synthesis genes. The synthesis of fatty acids is performed by the type II fatty acid biosynthesis pathway in eubacteria. There are four steps in the elongation cycle, which extends two carbons per cycle. In E. coli, the dehydration of the -hydroxyl-ACP is performed by FabA or FabZ. Unsaturated fatty acids are produced by the isomerase FabM, utilizing the fatty acid intermediate produced by FabZ, or directly by FabA, which has been shown to have an additional trans-2- to cis-3-decenoyl-ACP isomerase activity (Heath & Rock, 1996; Brock et al., 1967). FabZ, on the other hand, does not exhibit an isomerase activity, and is involved in both saturated and unsaturated fatty acid elongation. FabA is mainly found in Gram-negative bacteria that produce unsaturated fatty acids, while FabZ is found in most bacteria (Kimber et al., 2004). The 3D structures and the active sites have been determined for both FabA and FabZ. The active site residues determined from mutational studies are H70 and D84 for E. coli FabA (Leesong et al., 1996), and H133 and E147 for Plasmodium falciparum FabZ (Kostrewa et al., 2005).
We chose to mutate the conserved glutamates in the two AfsA repeat domains of ScbA. The other active site residues, histidine, in the fatty acid synthases was not conserved in the N-terminal domain of ScbA, but only in the C-terminal region, so this histidine was not mutated. The mutated C-terminal R243, on the other hand, was not conserved in the fatty acid synthase, but only in the AfsA repeat domains. The mutagenesis of either one or both conserved glutamate residues, or the arginine, abolished the production of -butyrolactones with antibiotic stimulatory activity. This strongly suggests that these amino acids are important for ScbA activity, indicating the HHpred prediction was indeed correct, and that ScbA is indeed an enzyme homologous to FabA and FabZ. The exact enzymic role of ScbA will need further biochemical analysis, but from the similarity of the active sites to FabA and FabZ, a dehydrase activity is probable, which is consistent with the proposed biosynthesis model of butyrolactones (Sakuda et al., 1992).
Using the 3D structures determined for FabA and FabZ, a structure of ScbA is proposed (Fig. 4). FabA and FabZ are homodimers (Leesong et al., 1996), and their two identical active sites are located at the dimer interface. We can assume that the two domains of ScbA will arrange in a similar fashion to form functional active sites. As the two domains have diverged considerably (pairwise sequence identity of 20 %), whereas the key residues remain unchanged (Fig. 1), it is probable that they catalyse similar reactions, but use different substrates.
|
), but, so far, from the S. coelicolor genome sequence, no obvious type II FabZ homologue has been identified (Bentley et al., 2002), while a distant orthologue has been found in Streptomyces avermitilis (Ikeda et al., 2003). Preliminary data suggest that S. coelicolor wild-type and the scbA mutant produce C14, C16 and C17 unsaturated fatty acid synthesis in SMMS (data not shown). This result may exclude the possibility of ScbA involvement in unsaturated fatty acids. However, the enzymes responsible for the synthesis of these fatty acids, i.e. the FabA or FabZ equivalent in S. coelicolor, have not been identified. A domain within a large multi-domain gene (SCO0127) has been found to have a weak similarity to FabZ. From the genome sequence of S. avermitilis, a similar multi-domain gene (SAV7361), which also has a FabA-homologous domain, was found, as well as an individual FabA (SAV3654, 31 % amino acid identity to E. coli FabA) and FabZ (SAV3655, 31 % amino acid identity) homologue. However, there are no other homologues of FabA or FabZ in S. coelicolor. Instead, we have identified a FabM homologue (SCO5144), which is also highly conserved in S. avermitilis (SAV3120, 86 % amino acid identity to SCO5144). In Streptococcus pneumoniae, a FabA homologue has not been identified, but a FabM homologue that encodes a trans-2, cis-3 decenoyl-ACP isomerase has been found, along with a FabZ homologue (Marrakchi et al., 2002). It is probable that SCO5144 is involved in the isomerase activity, but it is not clear what gene in S. coelicolor is responsible for the dehydration of -hydroxyacyl-ACP to produce branched fatty acids.
scbA is divergent to the -butyrolactone receptor gene scbR. SCO6264, located adjacent to scbR, also affects -butyrolactone synthesis in S. coelicolor (T. Nihira & E. Takano, unpublished). This gene is homologous to barS1, which is responsible for the reduction of the C-6 position of VBs in S. virginiae (Shikura et al., 2002). barS1 is also positioned close to barX on the chromosome; barX is the scbA homologue in S. virginiae. There were 10 scbA homologues, including scbA and barX, found in the NCBI database. Of these genes, nine have surrounding sequences available for analysis, and six of these possess homologous genes that probably encode members of the short-chain dehydrogenase family of proteins, which includes SCO6264 and the barS1 gene product. The genes adjacent to the afsA/scbA-like gene mmfL in S. coelicolor plasmid SCP1 and avaA in S. avermitilis, mmfH and SAV2267, respectively, are classified as medium-chain acyl-CoA dehydrogenases, and are somewhat distant from the others, but still have homology to dehydrogenases. The only exception to the ‘rule’ of having a dehydrogenase homologue in the cluster was S. griseus. This species is atypical, as the -butyrolactone receptor is at least 100 kb away from afsA, which is the scbA homologue (Ando et al., 1997). Considering the conservation of the position of these dehydrogenase homologues, it is possible that these genes are also involved in -butyrolactone synthesis, as in the case of barS1 and SCO6264. The differences in the dehydrogenase family may also be related to differences in the -butyrolactone precursor and end-product structures.
We have previously shown that the scbA deletion mutant overproduces antibiotics (Takano et al., 2001). In the present experiment, we were able to detect a slight difference in antibiotic production for all the strains using the integrative plasmid. This may be due to the integration of pSET152, which affects the production of the pigmented antibiotics, both positively and negatively; we observed this repeatedly even in the wild-type with the vector alone, and also the instability of the vector integration without selection (data not shown). To overcome this problem, RT-PCR was conducted on both the regulator and the biosynthesis genes. However, no difference was observed in the expression of the biosynthesis genes in any of the strains, and the expression of the regulators was variable. This is possibly due to the RNA isolated at a relatively late time point, which was too late to see a clear difference in the expression levels of the biosynthesis genes, as well as the effect of the integrated vector. To clearly determine the effect of the mutation on antibiotic production, we are currently introducing these mutations in ScbA into the chromosome.
We have also previously reported a possible regulatory function for ScbA (Takano et al., 2001), based on the observation that expression of scbA was not detected in the scbA mutant, and was not complemented by addition of SCB1. In the present work, the mutated ScbA proteins did not produce bioactive SCB proteins, but their expression under their own promoter, albeit in the 
C31 attachment site, was restored to the same level as the wild-type. This suggests that we have now uncoupled the regulatory function and the enzymic functions of ScbA, and this strengthens the possibility that ScbA has dual function.
|
NOTE ADDED IN PROOF |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONNOTE ADDED IN PROOFREFERENCES |
|---|
-butyrolactone produced by S. griseus, was published (Kato et al., 2007).
|
ACKNOWLEDGEMENTS |
|---|
Edited by: J. Anné
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONNOTE ADDED IN PROOFREFERENCES |
|---|
Ando, N., Matsumori, N., Sakuda, S., Beppu, T. & Horinouchi, S. (1997). Involvement of AfsA in A-factor biosynthesis as a key enzyme. J Antibiot 50, 847–852.[Medline]
Bentley, S. D., Chater, K. F., Cerdeno-Tarraga, A. M., Challis, G. L., Thomson, N. R., James, K. D., Harris, D. E., Quail, M. A., Kieser, H. & other authors (2002). Complete genome sequence of the model actinomycete Streptomyces coelicolor A3(2). Nature 417, 141–147.[CrossRef][Medline]
Bierman, M., Logan, R., O'Brien, K., Seno, E. T., Rao, R. N. & Schoner, B. E. (1992). Plasmid cloning vectors for the conjugal transfer of DNA from Escherichia coli to Streptomyces spp. Gene 116, 43–49.[CrossRef][Medline]
Brock, D. J., Kass, L. R. & Bloch, K. (1967). -hydroxydecanoyl thioester dehydrase. II. Mode of action. J Biol Chem 242, 4432–4440.
Camilli, A. & Bassler, B. L. (2006). Bacterial small-molecule signaling pathways. Science 311, 1113–1116.
Chiu, J., March, P. E., Lee, R. & Tillett, D. (2004). Site-directed, ligase-independent mutagenesis (SLIM): a single-tube methodology approaching 100 % efficiency in 4 h. Nucleic Acids Res 32, e174.
Chung, C. T., Niemela, S. L. & Miller, R. H. (1989). One-step preparation of competent Escherichia coli: transformation and storage of bacterial cells in the same solution. Proc Natl Acad Sci U S A 86, 2172–2175.
Flett, F., Mersinias, V. & Smith, C. P. (1997). High efficiency intergeneric conjugal transfer of plasmid DNA from Escherichia coli to methyl DNA-restricting streptomycetes. FEMS Microbiol Lett 155, 223–229.[CrossRef][Medline]
Gesheva, V., Rachev, R. & Bojkova, S. (1997). Fatty acid composition of Streptomyces hygroscopicus strains producing antibiotics. Lett Appl Microbiol 24, 109–112.[CrossRef][Medline]
Hara, O. & Beppu, T. (1982). Mutants blocked in streptomycin production in Streptomyces griseus – the role of A-factor. J Antibiot 35, 349–358.
Heath, R. J. & Rock, C. O. (1996). Roles of the FabA and FabZ -hydroxyacyl-acyl carrier protein dehydratases in Escherichia coli fatty acid biosynthesis. J Biol Chem 271, 27795–27801.
Horinouchi, S., Nishiyama, M., Suzuki, H., Kumada, Y. & Beppu, T. (1985). The cloned Streptomyces bikiniensis (griseus) A-factor determinant. J Antibiot 36, 636–641.
Ikeda, H., Ishikawa, J., Hanamoto, A., Shinose, M., Kikuchi, H., Shiba, T., Sakaki, Y., Hattori, M. & Omura, S. (2003). Complete genome sequence and comparative analysis of the industrial microorganism Streptomyces avermitilis. Nat Biotechnol 21, 526–531.[CrossRef][Medline]
Kato, J. Y., Funa, N., Watanabe, H., Ohnishi, Y. & Horinouchi, S. (2007). Biosynthesis of -butyrolactone autoregulators that switch on secondary metabolism and morphological development in Streptomyces. Proc Natl Acad Sci U S A 104, 2378–2383.
Kawachi, R., Akashi, T., Kamitani, Y., Sy, A., Wangchaisoonthorn, U., Nihira, T. & Yamada, Y. (2000). Identification of an a AfsA homologue (BarX) from Streptomyces virginiae as a pleiotropic regulator controlling autoregulator biosynthesis, virginiamycin biosynthesis and virginiamycin M1 resistance. Mol Microbiol 36, 302–313.[CrossRef][Medline]
Khokhlov, A. S., Tovarova, I. I., Borisova, L. N., Pliner, S. A., Shevchenko, L. A., Schevchenko, L. N., Kornitskaia, EIa., Ivkina, N. S. & Rapoport, I. A. (1967). The A-factor, responsible for streptomycin biosynthesis by mutant strains of Actinomyces streptomycini. Dokl Akad Nauk SSSR 177, 232–235.[Medline]
Kieser, T., Bibb, M. J., Buttner, M. J., Chater, K. F. & Hopwood, D. A. (2000). Practical Streptomyces Genetics. Norwich: John Innes Foundation.
Kimber, M. S., Martin, F., Lu, Y., Houston, S., Vedadi, M., Dharamsi, A., Fiebig, K. M., Schmid, M. & Rock, C. O. (2004). The structure of (3R)-hydroxyacyl-acylcarrier protein dehydratase (FabZ) from Pseudomonas aeruginosa. J Biol Chem 2793, 52593–52602.
Kostrewa, D., Winkler, F. K., Folkers, G., Scapozza, L. & Perozzo, R. (2005). The crystal structure of PfFabZ, the unique -hydroxyacyl-ACP dehydratase involved in fatty acid biosynthesis of Plasmodium falciparum. Protein Sci 14, 1570–1580.[CrossRef][Medline]
Leblond, P., Fischer, G., Francou, F. X., Berger, F., Guérineau, M. & Decaris, B. (1996). The unstable region of Streptomyces ambofaciens includes 210 kb terminal inverted repeats flanking the extremities of the linear chromosomal DNA. Mol Microbiol 19, 261–271.[CrossRef][Medline]
Leesong, M., Henderson, B. S., Gillig, J. R., Schwab, J. M. & Smith, J. L. (1996). Structure of a dehydratase-isomerase from the bacterial pathway for biosynthesis of unsaturated fatty acids: two catalytic activities in one active site. Structure 4, 253–264.[Medline]
MacNeil, D. J., Occi, J. L., Gewain, K. M., MacNeil, T., Gibbons, P. H., Ruby, C. L. & Danid, S. J. (1992). Complex organization of the Streptomyces avermitilis genes encoding the avermectin polyketide synthetase. Gene 155, 119–125.[CrossRef]
Marrakchi, H., Choi, K. H. & Rock, C. O. (2002). A new mechanism for anaerobic unsaturated fatty acid formation in Streptococcus pneumoniae. J Biol Chem 277, 44809–44816.
Murzin, A. G., Brenner, S. E., Hubbard, T. & Chothia, C. (1995). SCOP: a structural classification of proteins database for the investigation of sequences and structures. J Mol Biol 247, 536–540.[CrossRef][Medline]
Paget, M. S. B., Chamberlin, L., Atrih, A., Foster, S. J. & Buttner, M. J. (1999). Evidence that the extracytoplasmic function sigma factor 
E is required for normal cell wall structure in Streptomyces coelicolor A3(2). J Bacteriol 181, 204–211.
Sakuda, S., Higashi, A., Nihira, T. & Yamada, Y. (1990). Biosynthesis of virginiae butanolide A. J Am Chem Soc 112, 898–899.[CrossRef]
Sakuda, S., Higashi, A., Tanaka, S., Nihira, T. & Yamada, Y. (1992). Biosynthesis of virginiae butanolide A, a butyrolactone autoregulator from Streptomyces. J Am Chem Soc 114, 663–668.[CrossRef]
Sakuda, S., Tanaka, S., Mizuno, K., Sukcharoen, O., Nihira, T. & Yamada, Y. (1993). Biosynthetic studies on virginiae butanolide A, a butyrolactone autoregulator from Streptomyces. Part 2. Preparation of possible biosynthetic intermediates and conversion experiments in a cell-free system. J Chem Soc Perkin Trans 1, 2309–2315.
Sambrook, J., Fritsch, E. F. & Maniatis, T. (1989). Molecular Cloning: a Laboratory Manual, 2nd edn. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory.
Shikura, N., Yamamura, J. & Nihira, T. (2002). barS1, a gene for biosynthesis of a -butyrolactone autoregulator, a microbial signalling molecule eliciting antibiotic production in Streptomyces species. J Bacteriol 184, 5151–5157.
Söding, J., Biegert, A. & Lupas, A. N. (2005). The HHpred interactive server for protein homology detection and structure prediction. Nucleic Acids Res 33, W244–248.
Sonnhammer, E. L., Eddy, S. R., Birney, E., Bateman, A. & Durbin, R. (1998). Pfam: multiple sequence alignments and HMM-profiles of protein domains. Nucleic Acids Res 26, 320–322.
Strauch, E., Takano, E., Baylis, H. A. & Bibb, M. J. (1991). The stringent response in Streptomyces coelicolor A3(2). Mol Microbiol 5, 289–298.[Medline]
Takano, E. (2006). -Butyrolactones: Streptomyces signaling molecules regulating antibiotic production and differentiation. Curr Opin Microbiol 9, 287–294.[CrossRef][Medline]
Takano, E., Chakaraburtty, R., Nihira, T., Yamada, Y. & Bibb, M. J. (2001). A complex role for the -butyrolactone SCB1 in regulating antibiotic production in Streptomyces coelicolor A3(2). Mol Microbiol 41, 1015–1028.[CrossRef][Medline]
Takano, E., Kinoshita, H., Mersinias, V., Bucca, G., Hotchkiss, G., Nihira, T., Smith, C. P., Bibb, M., Wohlleben, W. & Chater, K. (2005). A bacterial hormone (the SCB1) directly controls the expression of a pathway-specific regulatory gene in the cryptic type I polyketide biosynthetic gene cluster of Streptomyces coelicolor. Mol Microbiol 56, 465–479.[CrossRef][Medline]
Vendeville, A., Winzer, K., Heurlier, K., Tang, C. M. & Hardie, K. R. (2005). Making ‘sense’ of metabolism: autoinducer-2, LuxS and pathogenic bacteria. Nature Rev Microbiol 3, 383–396.[CrossRef]
Venturi, V. (2006). Regulation of quorum sensing in Pseudomonas. FEMS Microbiol Rev 30, 274–291.[CrossRef][Medline]
Yamada, Y. (1999). Autoregulatory factors and regulation of antibiotic production in Streptomyces. In Microbial Signalling and Communication (Society for General Microbiology Symposium no. 57), pp. 177–196. Edited by R. R. England, G. Hobbs, N. J. Bainton & D. McL. Roberts. Cambridge: Cambridge University Press.
Received 18 November 2006;
revised 21 December 2006;
accepted 4 January 2007.
This article has been cited by other articles:
|
|
 |
|
  C. Corre, L. Song, S. O'Rourke, K. F. Chater, and G. L. Challis 2-Alkyl-4-hydroxymethylfuran-3-carboxylic acids, antibiotic production inducers discovered by Streptomyces coelicolor genome mining PNAS, November 11, 2008; 105(45): 17510 - 17515. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| INT J SYST EVOL MICROBIOL | MICROBIOLOGY | J GEN VIROL |
| J MED MICROBIOL | ALL SGM JOURNALS | |
), and mutants M751 : : pSET152 (
), M751 : : pIJ6147 (
), M751 : : pTE104 (
), M751 : : pTE106 (
), M751 : : pTE108 (
) and M751 : : pTE110 (
). Strains were grown in SMM liquid medium at 30 °C. At time points 18, 20, 22, 24 and 34 h, samples were collected to measure OD450. (b) 
