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cobaltochelatase, CobS subunit This 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. 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. 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. This model describes the aerobic cobalamin pathway Pseudomonas denitrificans CobS gene product, which is a cobalt chelatase subunit, with a MW ~37 kDa. 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 (pfam02514 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. [Biosynthesis of cofactors, prosthetic groups, and carriers, Heme, porphyrin, and cobalamin] |
Jiyao W et al.(2023). "The conserved domain database in 2023.",