This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases. The systematic name of this enzyme class is S-adenosyl-L-methionine:protein-L-glutamate O-methyltransferase. Other names in common use include methyl-accepting chemotaxis protein O-methyltransferase, S-adenosylmethionine-glutamyl methyltransferase, methyl-accepting chemotaxis protein methyltransferase II, S-adenosylmethionine:protein-carboxyl O-methyltransferase, protein methylase II, MCP methyltransferase I, MCP methyltransferase II, protein O-methyltransferase, protein(aspartate)methyltransferase, protein(carboxyl)methyltransferase, protein carboxyl-methylase, protein carboxyl-O-methyltransferase, protein carboxylmethyltransferase II, protein carboxymethylase, protein carboxymethyltransferase, and protein methyltransferase II. This enzyme participates in bacterial chemotaxis - general and bacterial chemotaxis - organism-specific.
Flagellated bacteria swim towards favourable chemicals and away from deleterious ones. Sensing of chemoeffector gradients involves chemotaxis receptors, transmembrane (TM) proteins that detect stimuli through their periplasmicdomains and transduce the signals via their cytoplasmicdomains .Signalling outputs from these receptors are influenced both by the binding of the chemoeffector ligand to their periplasmic domains and by methylation of specific glutamate residues on their cytoplasmic domains. Methylation is catalysed by CheR, an S-adenosylmethionine-dependent methyltransferase, which reversibly methylates specific glutamate residues within a coiled coil region, to form gamma-glutamyl methyl ester residues. The structure of the Salmonella typhimurium chemotaxis receptor methyltransferase CheR, bound to S-adenosylhomocysteine, has been determined to a resolution of 2.0 Angstrom. The structure reveals CheR to be a two-domain protein, with a smaller N-terminal helical domain linked via a single polypeptide connection to a larger C-terminal alpha/beta domain. The C-terminal domain has the characteristics of a nucleotide-binding fold, with an insertion of a small anti-parallel beta-sheet subdomain. The S-adenosylhomocysteine-binding site is formed mainly by the large domain, with contributions from residues within the N-terminal domain and the linker region.
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