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Beyond catalysis: vitamin B 12 as a cofactor in gene regulation
Author(s) -
Klug Gabriele
Publication year - 2014
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12490
Subject(s) - cofactor , biology , riboswitch , biochemistry , gene , myxococcus xanthus , regulation of gene expression , repressor , rhodobacter , b vitamins , function (biology) , gene expression , microbiology and biotechnology , enzyme , non coding rna , mutant , endocrinology
Summary Vitamin B 12 is well known as an enzyme cofactor in the catalysis of many important biological reactions, and the role of B 12 in regulation of bacterial gene expression as a ligand of riboswitches is well established. Only recently evidence has emerged that B 12 can also affect bacterial gene expression by acting as a cofactor of regulatory proteins. In 2011 a role of B 12 as a cofactor of the transcriptional repressor of carotenogenesis, CarH , in M yxococcus xanthus was reported. B 12 is required for light‐dependent DNA binding by CarH , which can therefore be considered to be a new type of photoreceptor. C heng et al . (2014) report the identification of B 12 as a cofactor of the AerR protein in R hodobacter capsulatus . AerR acts as an antirepressor of the CrtJ protein, which represses photosynthesis genes when binding to its target promoters. As in M yxococcus B 12 may have the role of a chromophore in photoreception, but it is suggested that a main function of AerR is the sensing of B 12 . The co‐regulation of the pathways is beneficial because the syntheses of B 12 , haem and bacteriochlorophylls share common precursors and the accumulation of the free molecules is toxic.