HMM Summary Page: TIGR01650

Functioncobaltochelatase, CobS subunit
Gene SymbolcobS
Trusted Cutoff558.55
Domain Trusted Cutoff558.55
Noise Cutoff140.70
Domain Noise Cutoff140.70
Isology Typeequivalog
EC Number6.6.1.2
HMM Length327
Mainrole CategoryBiosynthesis of cofactors, prosthetic groups, and carriers
Subrole CategoryHeme, porphyrin, and cobalamin
Gene Ontology TermGO:0009236: cobalamin biosynthetic process biological_process
GO:0051116: cobaltochelatase activity molecular_function
AuthorBeanan M
Entry DateAug 29 2002 9:32AM
Last ModifiedFeb 14 2011 3:27PM
CommentThis model describes Pseudomonas denitrificans CobS gene product, which is a cobalt chelatase subunit that functions in cobalamin biosynthesis. Cobalamin (vitamin B12) can be synthesized via several pathways, including an aerobic pathway (found in Pseudomonas denitrificans) and an anaerobic pathway (found in P. shermanii and Salmonella typhimurium). These pathways differ in the point of cobalt insertion during corrin ring formation [1]. There are apparently a number of variations on these two pathways, where the major differences seem to be concerned with the process of ring contraction [2]. Confusion regarding the functions of enzymes found in the aerobic vs. anaerobic pathways has arisen because nonhomologous genes in these different pathways were given the same gene symbols. Thus, cobS in the aerobic pathway (P. denitrificans) is not a homolog of cobS in the anaerobic pathway (S. typhimurium). It should be noted that E. coli synthesizes cobalamin only when it is supplied with the precursor cobinamide, which is a complex intermediate. Additionally, all E. coli cobalamin synthesis genes (cobU, cobS and cobT) were named after their Salmonella typhimurium homologs which function in the anaerobic cobalamin synthesis pathway [3]. This model describes the aerobic cobalamin pathway Pseudomonas denitrificans CobS gene product, which is a cobalt chelatase subunit, with a MW ~37 kDa [4]. The aerobic pathway cobalt chelatase is a heterotrimeric, ATP-dependent enzyme that catalyzes cobalt insertion during cobalamin biosynthesis. The other two subunits are the P. denitrificans CobT (TIGR01651) and CobN (PF02514 CobN/Magnesium Chelatase) proteins. To avoid potential confusion with the nonhomologous Salmonella typhimurium/E.coli cobS gene product, the P. denitrificans gene symbol is not used in the name of this model.
ReferencesRN [1] RM PMID: 8905078 RT Cobalamin (coenzyme B12): synthesis and biological significance. RA Roth,JR, Lawrence, JG, Bobik,TA RL Annu Rev Microbiol. 1996;50:137-81. RN [2] RM 11215515 RT Biosynthesis of cobalamin (vitamin B12): a bacterial conundrum. RA Raux E, Schubert HL, Warren MJ RT Cell Mol Life Sci. 2000 Dec;57(13-14):1880-93. RN [3] RM 7592411 RT The cobalamin (coenzyme B12) biosynthetic genes of Escherichia coli. RA Lawrence, JG, Roth JR RL J Bacteriol. 1995 Nov;177(22):6371-80. RN [4] RM 1429466 RT Assay, purification, and characterization of cobaltochelatase, a unique complex enzyme catalyzing cobalt insertion in hydrogenobyrinic acid a,c-diamide during coenzyme B12 biosynthesis in Pseudomonas denitrificans. RA Debussche, L, Couder, M, Thibault, D., Cameron, B., Crouzet, J. Blanche, F. RL J Bacteriol. 1992 Nov;174(22):7445-51.
Genome PropertyGenProp0113: cobyrinic acid diamide biosynthesis, aerobic pathway (HMM)