biology

Protein-glutamate O-methyltransferase

Protein-glutamate O-methyltransferase is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Protein-glutamate O-methyltransferase rather than just read about it. In short: In enzymology, a protein-glutamate O-methyltransferase (EC 2.1.1.80) is an enzyme that catalyzes the chemical reaction S-adenosyl-L-methionine + protein L-glutamate ⇌ {\displaystyle \rightleftharpoons } S-adenosyl-L-homocysteine + protein L-glutamate methyl ester Thus, the two substrates of this enzyme are S-adenosyl methionine and protein L-glutamic acid, whereas its two products are S-adenosylhomocysteine and prot…

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Reference excerpt

In enzymology, a protein-glutamate O-methyltransferase (EC 2.1.1.80) is an enzyme that catalyzes the chemical reaction

S-adenosyl-L-methionine + protein L-glutamate ⇌ {\displaystyle \rightleftharpoons } S-adenosyl-L-homocysteine + protein L-glutamate methyl ester Thus, the two substrates of this enzyme are S-adenosyl methionine and protein L-glutamic acid, whereas its two products are S-adenosylhomocysteine and protein L-glutamate methyl ester. 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 chemotaxisl. 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 PDB: 1AF7 and PDB: 1BC5.

References

Further reading 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.

Illustrations

Worked examples

Example 1 — a first encounter with Protein-glutamate O-methyltransferase

Start with the simplest possible case. Write down what Protein-glutamate O-methyltransferase claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Protein-glutamate O-methyltransferase before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Protein-glutamate O-methyltransferase ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Protein-glutamate O-methyltransferase

In research: Protein-glutamate O-methyltransferase appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Protein-glutamate O-methyltransferase in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Protein-glutamate O-methyltransferase is common in secondary-school and first-year university syllabi. It links to neighbouring topics EC 2.1.1, Enzymes of known structure, Protein domains, so understanding it makes those chapters shorter.
In everyday life: Look for Protein-glutamate O-methyltransferase outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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Frequently asked questions

What is Protein-glutamate O-methyltransferase in simple terms?

In enzymology, a protein-glutamate O-methyltransferase (EC 2.1.1.80) is an enzyme that catalyzes the chemical reaction S-adenosyl-L-methionine + protein L-glutamate ⇌ {\displaystyle \rightleftharpoons } S-adenosyl-L-homocysteine + protein L-glutamate methyl ester Thus, the two substrates of this en…

Why does Protein-glutamate O-methyltransferase matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

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