1af7
From Proteopedia
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CHER FROM SALMONELLA TYPHIMURIUM
Overview
BACKGROUND: Flagellated bacteria swim towards favorable chemicals and away, from deleterious ones. The sensing of chemoeffector gradients involves, chemotaxis receptors, transmembrane proteins that detect stimuli through, their periplasmic domains and transduce signals via their cytoplasmic, domains to the downstream signaling components. Signaling outputs from, chemotaxis receptors are influenced both by the binding of the, chemoeffector ligand to the periplasmic domain and by methylation of, specific glutamate residues on the cytoplasmic domain of the receptor., Methylation is catalyzed by CheR, an S-adenosylmethionine-dependent, methyltransferase. CheR forms a tight complex with the receptor by binding, a region of the receptors that is distinct from the methylation site. CheR, belongs to a broad class of enzymes involved in the methylation of a, variety of substrates. Until now, no structure from the class of protein, methyltransferases has been characterized. RESULTS: The structure of the, Salmonella typhimurium chemotaxis receptor methyltransferase CheR bound to, S-adenosylhomocysteine, a product and inhibitor of the methylation, reaction, has been determined at 2.0 A resolution. The structure reveals, CheR to be a two-domain protein, with a smaller N-terminal helical domain, linked through 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 antiparallel 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. CONCLUSIONS: The CheR structure, shares some structural similarities with small molecule DNA and RNA, methyltransferases, despite a lack of sequence similarity among them. In, particular, there is significant structural preservation of the, S-adenosylmethionine-binding clefts; the specific length and conformation, of a loop in the alpha/beta domain seems to be required for, S-adenosylmethionine binding within these enzymes. Unique structural, features of CheR, such as the beta subdomain, are probably necessary for, CheR's specific interaction with its substrates, the bacterial chemotaxis, receptors.
About this Structure
1AF7 is a Single protein structure of sequence from Salmonella typhimurium with SAH as ligand. Active as Protein-glutamate O-methyltransferase, with EC number 2.1.1.80 Full crystallographic information is available from OCA.
Reference
Crystal structure of the chemotaxis receptor methyltransferase CheR suggests a conserved structural motif for binding S-adenosylmethionine., Djordjevic S, Stock AM, Structure. 1997 Apr 15;5(4):545-58. PMID:9115443
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