Protein-glutamate O-methyltransferase

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.

CheR proteins are part of the chemotaxis signaling mechanism which methylates the chemotaxis receptor at specific glutamate residues. Methyl transfer from the ubiquitous S-adenosyl-L-methionine (AdoMet/SAM) to either nitrogen, oxygen or carbon atoms is frequently employed in diverse organisms ranging from bacteria to plants and mammals. The reaction is catalysed by methyltransferases (Mtases) and modifies DNA, RNA, proteins and small molecules, such as catechol for regulatory purposes. The various aspects of the role of DNA methylation in prokaryotic restriction-modification systems and in a number of cellular processes in eukaryotes including gene regulation and differentiation is well documented.

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 . 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.

Structural studies

As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes 1AF7 and 1BC5.

References

^ Djordjevic S, Stock AM (April 1997). "Crystal structure of the chemotaxis receptor methyltransferase CheR suggests a conserved structural motif for binding S-adenosylmethionine". Structure. 5 (4): 545–58. doi:10.1016/S0969-2126(97)00210-4. PMID 9115443.
Djordjevic S, Stock AM (June 1998). "Chemotaxis receptor recognition by protein methyltransferase CheR". Nat. Struct. Biol. 5 (6): 446–50. doi:10.1038/nsb0698-446. PMID 9628482. S2CID 28557040.

Burgess-Cassler A, Ullah AH, Ordal GW (1982). "Purification and characterization of Bacillus subtilis methyl-accepting chemotaxis protein methyltransferase II". J. Biol. Chem. 257 (14): 8412–7. doi:10.1016/S0021-9258(18)34347-3. PMID 6806296.
Kleene SJ, Toews ML, Adler J (1977). "Isolation of glutamic acid methyl ester from an Escherichia coli membrane protein involved in chemotaxis". J. Biol. Chem. 252 (10): 3214–8. doi:10.1016/S0021-9258(17)40373-5. PMID 16888.
Simms SA, Stock AM, Stock JB (1987). "Purification and characterization of the S-adenosylmethionine:glutamyl methyltransferase that modifies membrane chemoreceptor proteins in bacteria". J. Biol. Chem. 262 (18): 8537–43. doi:10.1016/S0021-9258(18)47447-9. PMID 3298235.
Springer WR, Koshland DE (1977). "Identification of a protein methyltransferase as the cheR gene product in the bacterial sensing system". Proc. Natl. Acad. Sci. U.S.A. 74 (2): 533–7. Bibcode:1977PNAS...74..533S. doi:10.1073/pnas.74.2.533. PMC 392324. PMID 322131.

Transferase: one carbon transferases (EC 2.1)

2.1.1: Methyl-

N-	Histamine N-methyltransferase Phenylethanolamine N-methyltransferase Amine N-methyltransferase Phosphatidylethanolamine N-methyltransferase
O-	5-hydroxyindole-O-methyltransferase/Acetylserotonin O-methyltransferase Catechol-O-methyl transferase
Homocysteine	Betaine-homocysteine methyltransferase Homocysteine methyltransferase Methionine synthase
Other	Phosphatidyl ethanolamine methyltransferase DNMT3B Histone methyltransferase Thymidylate synthase DNA methyltransferase Thiopurine methyltransferase Cyclopropane-fatty-acyl-phospholipid synthase

2.1.2: Hydroxymethyl-,
Formyl- and Related

Hydroxymethyltransferase	Serine hydroxymethyltransferase 3-methyl-2-oxobutanoate hydroxymethyltransferase
Formyltransferase	Phosphoribosylglycinamide formyltransferase Inosine monophosphate synthase
Other	Glutamate formimidoyltransferase Aminomethyltransferase

2.1.3: Carboxy-
and Carbamoyl

Carboxy	methylmalonyl-CoA carboxytransferase
Carbamoyl	Aspartate carbamoyltransferase Ornithine carbamoyltransferase Oxamate carbamoyltransferase Putrescine carbamoyltransferase 3-hydroxymethylcephem carbamoyltransferase Lysine carbamoyltransferase N-acetylornithine carbamoyltransferase

2.1.4: Amidine

Arginine:glycine amidinotransferase

v t e Enzymes
Activity	Active site Binding site Catalytic triad Oxyanion hole Enzyme promiscuity Diffusion-limited enzyme Cofactor Enzyme catalysis
Regulation	Allosteric regulation Cooperativity Enzyme inhibitor Enzyme activator
Classification	EC number Enzyme superfamily Enzyme family List of enzymes
Kinetics	Enzyme kinetics Eadie–Hofstee diagram Hanes–Woolf plot Lineweaver–Burk plot Michaelis–Menten kinetics
Types	EC1 Oxidoreductases (list) EC2 Transferases (list) EC3 Hydrolases (list) EC4 Lyases (list) EC5 Isomerases (list) EC6 Ligases (list) EC7 Translocases (list)

Portal:

Biology

This article incorporates text from the public domain Pfam and InterPro: IPR022641 This article incorporates text from the public domain Pfam and InterPro: IPR022642 Categories:

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