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Genetics and Molecular Biology |
Department of Biology, Dalhousie University, Halifax, Nova Scotia, CanadaB3H 4J11
Author for correspondence: L. C. Vining. Tel: +1 902 494 2040. Fax: +1 902 494 3736. e-mail: Leo.Vining{at}Dal.Ca
Amplification of sequences from Streptomyces venezuelae ISP5230 genomic DNA using PCR with primers based on conserved prokaryotic pabB sequences gave two main products. One matched pabAB, a locus previously identified in S. venezuelae. The second closely resembled the conserved pabB sequence consensus and hybridized with a 3·8 kb NcoI fragment of S. venezuelae ISP5230 genomic DNA. Cloning and sequence analysis of the 3·8 kb fragment detected three ORFs, and their deduced amino acid sequences were used in BLAST searches of the GenBank database. The ORF1 product was similar to PabB in other bacteria and to the PabB domain encoded by S. venezuelae pabAB. The ORF2 product resembled PabA of other bacteria. ORF3 was incomplete; its deduced partial amino acid sequence placed it in the MocR group of GntR-type transcriptional regulators. Introducing vectors containing the 3·8 kb NcoI fragment of S. venezuelae DNA into pabA and pabB mutants of Escherichia coli, or into the Streptomyces lividans pab mutant JG10, enhanced sulfanilamide resistance in the host strains. The increased resistance was attributed to expression of the pair of discrete translationally coupled p-aminobenzoic acid biosynthesis genes (designated pabB/pabA) cloned in the 3·8 kb fragment. These represent a second set of genes encoding 4-amino-4-deoxychorismate synthase in S. venezuelae ISP5230. In contrast to the fused pabAB set previously isolated from this species, they do not participate in chloramphenicol biosynthesis, but like pabAB they can be disrupted without affecting growth on minimal medium. The gene disruption results suggest that S. venezuelae may have a third set of genes encoding PABA synthase.
Keywords: p-aminobenzoate synthase genes, primary and secondary metabolism
Abbreviations: ADC, 4-amino-4-deoxychorismic acid; PABA, p-aminobenzoic acid; PAPA, p-aminophenylalanine; Am, apramycin; Cm, chloramphenicol; Ts, thiostrepton; Vio, viomycin
The GenBank accession number for the sequence reported in this paper is AF189258.
a Present address: Microbiology Department, University of Minnesota, 1030 Mayo Building, 420 Delaware Street SE, Minneapolis, MN 55455, USA.
b Present address: Pharmaceutics Department, Pharmacy University of Shenyang, 103 Wenhua Rd, Shenyang, P.R. China.
This article has been cited by other articles:
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  M. Piraee, R. L. White, and L. C. Vining Biosynthesis of the dichloroacetyl component of chloramphenicol in Streptomyces venezuelae ISP5230: genes required for halogenation Microbiology, January 1, 2004; 150(1): 85 - 94. [Abstract] [Full Text] [PDF]
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L. Wang and L. C. Vining Control of growth, secondary metabolism and sporulation in Streptomyces venezuelae ISP5230 by jadW1, a member of the afsA family of {gamma}-butyrolactone regulatory genes Microbiology, August 1, 2003; 149(8): 1991 - 2004. [Abstract] [Full Text] [PDF]
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Z. Chang and L. C. Vining Biosynthesis of sulfur-containing amino acids in Streptomyces venezuelae ISP5230: roles for cystathionine {beta}-synthase and transsulfuration Microbiology, July 1, 2002; 148(7): 2135 - 2147. [Abstract] [Full Text] [PDF]
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L. Wang, R. L. White, and L. C. Vining Biosynthesis of the dideoxysugar component of jadomycin B: genes in the jad cluster of Streptomyces venezuelae ISP5230 for L-digitoxose assembly and transfer to the angucycline aglycone Microbiology, April 1, 2002; 148(4): 1091 - 1103. [Abstract] [Full Text] [PDF]
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