Summary: Cobalt chelatase (CbiK)
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Cobalt chelatase (CbiK) Provide feedback
This family consists of several bacterial cobalt chelatase (CbiK) proteins ( EC:4.99.1.-).
Raux E, Thermes C, Heathcote P, Rambach A, Warren MJ; , J Bacteriol 1997;179:3202-3212.: A role for Salmonella typhimurium cbiK in cobalamin (vitamin B12) and siroheme biosynthesis. PUBMED:9150215 EPMC:9150215
Internal database links
|Similarity to PfamA using HHSearch:||CbiX Ferrochelatase|
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR010388
Cobalamin (vitamin B12) can be complexed with metal via ATP-dependent reactions (aerobic pathway) (e.g., in Pseudomonas denitrificans) or via ATP-independent reactions (anaerobic pathway) (e.g., in S. typhimurium) [PUBMED:8905078, PUBMED:11469861]. The corresponding cobalt chelatases are not homologous. This group belongs to the class of ATP-independent, single-subunit chelatases that also includes distantly related protoporphyrin IX (PPIX) ferrochelatase (HemH) (Class II chelatases) [PUBMED:12686546]. The structure of S. typhimurium CbiK shows that it has a remarkably similar topology to Bacillus subtilis ferrochelatase despite only weak sequence conservation [PUBMED:10451360]. Both enzymes contain a histidine residue identified as the metal ion ligand, but CbiK contains a second histidine in place of the glutamic acid residue identified as a general base in PPIX ferrochelatase [PUBMED:10451360]. Site-directed mutagenesis has confirmed a role for this histidine and a nearby glutamic acid in cobalt binding, modulating metal ion specificity as well as catalytic efficiency [PUBMED:10451360].
It should be noted that CysG and Met8p, which are multifunctional proteins associated with siroheme biosynthesis, include chelatase activity and can therefore be considered as the third class of chelatases [PUBMED:12686546]. As with the class II chelatases, they do not require ATP for activity. However, they are not structurally similar to HemH or CbiK, and it is likely that they have arisen by the acquisition of a chelatase function within a dehydrogenase catalytic framework [PUBMED:11980703, PUBMED:12686546].
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|Molecular function||sirohydrochlorin cobaltochelatase activity (GO:0016852)|
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Curation and family details
|Seed source:||Pfam-B_10975 (release 9.0)|
|Number in seed:||8|
|Number in full:||718|
|Average length of the domain:||247.40 aa|
|Average identity of full alignment:||37 %|
|Average coverage of the sequence by the domain:||87.61 %|
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build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 23193494 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||6|
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For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the CbiK domain has been found. There are 5 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.
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