PROSITE documentation PDOC50123

CheR-type methyltransferase profile

Chemotaxis in bacteria is a behavourial response that allows bacteria to migrate towards favorable chemicals and away from unfavorable ones. The signaling activity of bacterial chemotaxis transmembrane receptors is modulated by reversible methylation of specific glutamate residues predicted to lie within a coiled-coil region of the receptors cytoplasmic domain. The level of receptor methylation results from the activities of a specific S-adenosyl-L-methionine-dependent methyltransferase (EC 2.1.1.80), CheR, and CheB methylesterase (see <PDOC50122>) [1,2]. The CheR methyltransferase binds to major chemoreceptors through their C-terminal pentapeptide motif NWETF, which is distinct from the methylation site.

The crystal structure reveals CheR to be a mixed α/β two-domain protein. The N-terminal domain consists of four α-helices while the C-terminal domain has a modified Rossmann-type fold. The central seven-stranded β-sheet in the C-terminal domain of CheR is commonly found in all S-adenosylmethionine-dependent methyltransferases. However, the C-terminal domain of CheR deviates from this common fold by insertion of a subdomain (β-subdomain) consisting of a three-stranded β-sheet and an α-helix. The β-subdomain of the CheR methyltransferase is a unique protein-protein interaction structural unit found specifically in methyltransferases associated with bacterial receptors. The protein-protein recognition involving this subdomain occurs through extension of the β-sheet of the methyltransferase by addition of a β-strand originating from the C-termini of some chemotaxis receptors [3,4].

The profile we developed covers the entire CheR methyltransferase.