Taxonomic distribution of proteins containing CobW_C domains

The tree below includes only several representative species and genera. The complete taxonomic breakdown of all proteins containing CobW_C domains can be accessed here. Click the counts or percentage values to display the corresponding proteins.

Comparative genomics of the vitamin B12 metabolism and regulation inprokaryotes.

Rodionov DA, Vitreschak AG, Mironov AA, Gelfand MS
J Biol Chem. 2003; 278: 41148-59

Using comparative analysis of genes, operons, and regulatory elements, wedescribe the cobalamin (vitamin B12) biosynthetic pathway in availableprokaryotic genomes. Here we found a highly conserved RNA secondarystructure, the regulatory B12 element, which is widely distributed in theupstream regions of cobalamin biosynthetic/transport genes in eubacteria.In addition, the binding signal (CBL-box) for a hypothetical B12 regulatorwas identified in some archaea. A search for B12 elements and CBL-boxesand positional analysis identified a large number of new candidateB12-regulated genes in various prokaryotes. Among newly assigned functionsassociated with the cobalamin biosynthesis, there are several new types ofcobalt transporters, ChlI and ChlD subunits of the CobN-dependentcobaltochelatase complex, cobalt reductase BluB, adenosyltransferase PduO,several new proteins linked to the lower ligand assembly pathway,l-threonine kinase PduX, and a large number of other hypotheticalproteins. Most missing genes detected within the cobalamin biosyntheticpathways of various bacteria were identified as nonorthologoussubstitutes. The variable parts of the cobalamin metabolism appear to bethe cobalt transport and insertion, the CobG/CbiG- and CobF/CbiD-catalyzedreactions, and the lower ligand synthesis pathway. The most interestingresult of analysis of B12 elements is that B12-independent isozymes of themethionine synthase and ribonucleotide reductase are regulated by B12elements in bacteria that have both B12-dependent and B12-independentisozymes. Moreover, B12 regulons of various bacteria are thought toinclude enzymes from known B12-dependent or alternative pathways.

Nitrile hydratase gene from Rhodococcus sp. N-774 requirement for itsdownstream region for efficient expression.

Hashimoto Y, Nishiyama M, Horinouchi S, Beppu T
Biosci Biotechnol Biochem. 1994; 58: 1859-65

For improvement of the production of nitrile hydratase (NHase) fromRhodococcus sp. N-774 by recombinant DNA techniques, several plasmids,each of which had a deletion of the upstream or downstream region of thegenes encoding the alpha and beta subunits of NHase, were constructed.Enzyme assays of recombinant R. rhodochrous and Escherichia coli cellsshowed that a downstream region of the NHase genes was indispensable forthe production of active NHase in both cells, but for the production ofthe active amidase, no genes other than the amidase structural gene wererequired. The nucleotide sequence of the downstream region contained asingle open reading frame (Orf1188) with 396 amino acids. Orf1188 showedsimilarity in amino acid sequence to P47K, an open reading frame founddownstream of the NHase genes from Pseudomonas chlororaphis B23, and alsoto the cobW gene product, which may be involved in cobalamin biosynthesisin Pseudomonas denitrificans. Because the distance between the TGA stopcodon for the NHase beta-subunit and the ATG codon for Orf1188 is only 98bp, and because production of both Orf1188 and NHase is dependent on apromoter upstream of the amidase gene, these genes appear to beco-transcribed in a polycistronic manner, forming an operon. Byoptimization of the culture conditions of R. rhodochrous carrying pKRNH2,which contained the amidase, NHase, and Orf1188 genes, the transformantshowed the NHase activity 6-fold higher than that of the original strain,Rhodococcus sp. N-774.