1e6y

From Proteopedia

Revision as of 07:37, 3 February 2008

METHYL-COENZYME M REDUCTASE FROM METHANOSARCINA BARKERI

Overview

The nickel enzyme methyl-coenzyme M reductase (MCR) catalyzes the terminal, step of methane formation in the energy metabolism of all methanogenic, archaea. In this reaction methyl-coenzyme M and coenzyme B are converted, to methane and the heterodisulfide of coenzyme M and coenzyme B. The, crystal structures of methyl-coenzyme M reductase from Methanosarcina, barkeri (growth temperature optimum, 37 degrees C) and Methanopyrus, kandleri (growth temperature optimum, 98 degrees C) were determined and, compared with the known structure of MCR from Methanobacterium, thermoautotrophicum (growth temperature optimum, 65 degrees C). The active, sites of MCR from M. barkeri and M. kandleri were almost identical to that, of M. thermoautotrophicum and predominantly occupied by coenzyme M and, coenzyme B. The electron density at 1.6 A resolution of the M. barkeri, enzyme revealed that four of the five modified amino acid residues of MCR, from M. thermoautotrophicum, namely a thiopeptide, an S-methylcysteine, a, 1-N-methylhistidine and a 5-methylarginine were also present. Analysis of, the environment of the unusual amino acid residues near the active site, indicates that some of the modifications may be required for the enzyme to, be catalytically effective. In M. thermoautotrophicum and M. kandleri high, temperature adaptation is coupled with increasing intracellular, concentrations of lyotropic salts. This was reflected in a higher fraction, of glutamate residues at the protein surface of the thermophilic enzymes, adapted to high intracellular salt concentrations.

About this Structure

1E6Y is a Protein complex structure of sequences from Methanosarcina barkeri with , , and as ligands. Known structural/functional Sites: and . Full crystallographic information is available from OCA.

Reference

Comparison of three methyl-coenzyme M reductases from phylogenetically distant organisms: unusual amino acid modification, conservation and adaptation., Grabarse W, Mahlert F, Shima S, Thauer RK, Ermler U, J Mol Biol. 2000 Oct 20;303(2):329-44. PMID:11023796

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