CheR proteins are part of the chemotaxis signaling mechanism in bacteria. 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 periplasmic domains and transduce the signals via their cytoplasmic domains [ PUBMED:9115443 … expand

CheR proteins are part of the chemotaxis signaling mechanism in bacteria. 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 periplasmic domains and transduce the signals via their cytoplasmic domains [ PUBMED:9115443 ]. 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 [ PUBMED:9115443 ], which reversibly methylates specific glutamate residues within a coiled coil region, to form gamma-glutamyl methyl ester residues [ PUBMED:9115443 PUBMED:9628482 ].

The structure of the Salmonella typhimurium chemotaxis receptor methyltransferase CheR, bound to S-adenosylhomocysteine, has been determined to a resolution of 2.0 A [ PUBMED:9115443 ]. 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 α/β domain. The C-terminal domain has the characteristics of a nucleotide-binding fold, with an insertion of a small anti-parallel β-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 [ PUBMED:9115443 ].