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J Bacteriol, March 1998, p. 1119-1128, Vol. 180, No. 5
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.

Helicobacter pylori porCDAB and oorDABC Genes Encode Distinct Pyruvate:Flavodoxin and 2-Oxoglutarate:Acceptor Oxidoreductases Which Mediate Electron Transport to NADP

Nicky J. Hughes,1 Chris L. Clayton,2 Peter A. Chalk,2 and David J. Kelly1,*

Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN,1 and Glaxo-Wellcome Ltd., Stevenage, Herts SG1 2NY,2 United Kingdom

Received 4 September 1997/Accepted 17 December 1997

Helicobacter pylori, a major cause of human gastric disease, is a microaerophilic bacterium that contains neither pyruvate nor 2-oxoglutarate dehydrogenase activity. Previous studies (N. J. Hughes, P. A. Chalk, C. L. Clayton, and D. J. Kelly, J. Bacteriol. 177:3953-3959, 1995) have indicated that the major routes for the generation of acetyl coenzyme A (acetyl-CoA) and succinyl-CoA are via pyruvate:flavodoxin oxidoreductase (POR) and 2-oxoglutarate:acceptor oxidoreductase (OOR), respectively. The purified POR is a heterotetrameric protein, with subunits of 48 (PorA), 36 (PorB), 24 (PorC), and 14 (PorD) kDa. In this study OOR has been purified, and it is similarly composed of polypeptides of 43 (OorA), 33 (OorB), 24 (OorC), and 10 (OorD) kDa. Both POR and OOR are oxygen labile and are likely to be major contributors to the microaerophilic phenotype of H. pylori. Unlike POR, OOR was unable to use a previously identified flavodoxin (FldA) as an electron acceptor. Although the purified enzymes were unable to reduce NAD(P), electrons from both pyruvate and 2-oxoglutarate could reduce NADP in cell extracts, consistent with a role for these oxidoreductases in the provision of NADPH as a respiratory electron donor. The H. pylori por, oor, and fldA genes were cloned and sequenced. The deduced por gene products showed significant sequence similarity to archaeal four-subunit 2-oxoacid:acceptor oxidoreductases. However, the amino acid sequences of OorA and -B were more closely related to that of the two-subunit POR of the aerobic halophile Halobacterium halobium. Both porD and oorD encode integral ferredoxin-like subunits. POR and OOR are probably essential enzymes in H. pylori, as insertion inactivation of porB and oorA appeared to be lethal.

* Corresponding author. Mailing address: Department of Molecular Biology and Biotechnology, University of Sheffield, P.O. Box 594, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom. Phone: 44 114 222 4414. Fax: 44 114 272 8697. E-mail: d.kelly{at}sheffield.ac.uk.




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