HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Jolley, K. A. Articles by Danson, M. J. Search for Related Content PubMed PubMed Citation Articles by Jolley, K. A. Articles by Danson, M. J. Agricola Articles by Jolley, K. A. Articles by Danson, M. J.

2-Oxoacid dehydrogenase multienzyme complexes in the halophilic Archaea? Gene sequences and protein structural predictions

Centre for Extremophile Research, Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK¹
Department of Microbiology & Immunology, University of Melbourne, Parkville, Australia²

Author for correspondence: Michael J. Danson. Tel: +44 1225 826509. Fax: +44 1225 826779. e-mail: M.J.Danson{at}bath.ac.uk

All Archaea catalyse the conversion of pyruvate to acetyl-CoA via a simple pyruvate oxidoreductase. This is in contrast to the Eukarya and most aerobic bacteria, which use the pyruvate dehydrogenase multienzyme complex [PDHC], consisting of multiple copies of three component enzymes: E1 (pyruvate decarboxylase), E2 (lipoate acetyl-transferase) and E3 (dihydrolipoamide dehydrogenase, DHLipDH). Until now no PDHC activity has been found in the Archaea, although DHLipDH has been discovered in the extremely halophilic Archaea and its gene sequence has been determined. In this paper, the discovery and sequencing of an operon containing the DHLipDH gene in the halophilic archaeon Haloferax volcanii are reported. Upstream of the DHLipDH gene are 3 ORFs which show highest sequence identities with the E1, E1ß and E2 genes of the PDHC from Gram-positive organisms. Structural predictions of the proposed protein product of the E2 gene show a domain structure characteristic of the E2 component in PDHCs, and catalytically important residues, including the lysine to which the lipoic acid cofactor is covalently bound, are conserved. Northern analyses indicate the transcription of the whole operon, but no PDHC enzymic activity could be detected in cell extracts. The presence in the E2 gene of an insertion (equivalent to approximately 100 aa) not found in bacterial or eukaryal E2 proteins, might be predicted to prevent multienzyme complex assembly. This is the first detailed report of the genes for a putative 2-oxoacid dehydrogenase complex in the Archaea, and the evolutionary and metabolic consequences of these findings are discussed.

Keywords: halophile, central metabolism, pyruvate dehydrogenase complex, dihydrolipoamide dehydrogenase

Abbreviations: BCODHC, branched-chain 2-oxoacid dehydrogenase complex; DHLipDH, dihydrolipoamide dehydrogenase; ODHC, 2-oxoacid dehydrogenase complex; OGDHC, 2-oxoglutarate dehydrogenase complex; PDHC, pyruvate dehydrogenase complex; TPP, thiamine pyrophosphate

The GenBank accession number for the sequence reported in this paper is AF068743.

This article has been cited by other articles:

				J. van Ooyen and J. Soppa Three 2-oxoacid dehydrogenase operons in Haloferax volcanii: expression, deletion mutants and evolution Microbiology, October 1, 2007; 153(10): 3303 - 3313. [Abstract] [Full Text] [PDF]

				A. Price-Whelan, L. E. P. Dietrich, and D. K. Newman Pyocyanin Alters Redox Homeostasis and Carbon Flux through Central Metabolic Pathways in Pseudomonas aeruginosa PA14 J. Bacteriol., September 1, 2007; 189(17): 6372 - 6381. [Abstract] [Full Text] [PDF]

				P. A. Kirkland, C. J. Reuter, and J. A. Maupin-Furlow Effect of proteasome inhibitor clasto-lactacystin-beta-lactone on the proteome of the haloarchaeon Haloferax volcanii Microbiology, July 1, 2007; 153(7): 2271 - 2280. [Abstract] [Full Text] [PDF]

				C. Wanner and J. Soppa Functional Role for a 2-Oxo Acid Dehydrogenase in the Halophilic Archaeon Haloferax volcanii J. Bacteriol., June 1, 2002; 184(11): 3114 - 3121. [Abstract] [Full Text] [PDF]

				S. T. Fitz-Gibbon, H. Ladner, U.-J. Kim, K. O. Stetter, M. I. Simon, and J. H. Miller Genome sequence of the hyperthermophilic crenarchaeon Pyrobaculum aerophilum PNAS, January 9, 2002; (2002) 241636498. [Abstract] [Full Text] [PDF]

				W. V. Ng, S. P. Kennedy, G. G. Mahairas, B. Berquist, M. Pan, H. D. Shukla, S. R. Lasky, N. S. Baliga, V. Thorsson, J. Sbrogna, et al. Genome sequence of Halobacterium species NRC-1 PNAS, September 29, 2000; (2000) 190337797. [Abstract] [Full Text]

				W. V. Ng, S. P. Kennedy, G. G. Mahairas, B. Berquist, M. Pan, H. D. Shukla, S. R. Lasky, N. S. Baliga, V. Thorsson, J. Sbrogna, et al. From the Cover: Genome sequence of Halobacterium species NRC-1 PNAS, October 24, 2000; 97(22): 12176 - 12181. [Abstract] [Full Text] [PDF]

				S. T. Fitz-Gibbon, H. Ladner, U.-J. Kim, K. O. Stetter, M. I. Simon, and J. H. Miller Genome sequence of the hyperthermophilic crenarchaeon Pyrobaculum aerophilum PNAS, January 22, 2002; 99(2): 984 - 989. [Abstract] [Full Text] [PDF]