title: Didehydroaspartate Modification in Methyl-Coenzyme M Reductase Catalyzing Methane Formation.
abstract: All methanogenic and methanotrophic archaea known to date contain methyl-coenzyme M reductase (MCR) that catalyzes the reversible reduction of methyl-coenzyme M to methane. This enzyme contains the nickel porphinoid F430 as a prosthetic group and, highly conserved, a thioglycine and four methylated amino acid residues near the active site. We describe herein the presence of a novel post-translationally modified amino acid, didehydroaspartate, adjacent to the thioglycine as revealed by mass spectrometry and high-resolution X-ray crystallography. Upon chemical reduction, the didehydroaspartate residue was converted into aspartate. Didehydroaspartate was found in MCR I and II from Methanothermobacter marburgensis and in MCR of phylogenetically distantly related Methanosarcina barkeri but not in MCR I and II of Methanothermobacter wolfeii, which indicates that didehydroaspartate is dispensable but might have a role in fine-tuning the active site to increase the catalytic efficiency.
authors.affiliation: Max-Planck-Institut für terrestrische Mikrobiologie, Karl-von-Frisch-Strasse 10, 35043, Marburg, Germany.
authors.forename: Tristan
authors.initials: T
authors.lastname: Wagner
authors.affiliation: Max-Planck-Institut für terrestrische Mikrobiologie, Karl-von-Frisch-Strasse 10, 35043, Marburg, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Kahnt
authors.affiliation: Max-Planck-Institut für Biophysik, Max-von-Laue-Strasse 3, 60438, Frankfurt/Main, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Ermler
authors.affiliation: Max-Planck-Institut für terrestrische Mikrobiologie, Karl-von-Frisch-Strasse 10, 35043, Marburg, Germany. shima@mpi-marburg.mpg.de.|CREST, Japan Science and Technology Agency (JST), Saitama, 332-0012, Japan. shima@mpi-marburg.mpg.de.
authors.forename: Seigo
authors.initials: S
authors.lastname: Shima
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D008697:Methane / Q000378:metabolism*; D017013:Methanobacteriaceae / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D017021:Methanosarcina barkeri / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D011499:Protein Processing, Post-Translational
chemical_list: D010088:Oxidoreductases; C021572:methyl coenzyme M reductase; D008697:Methane
keywords: didehydroaspartate; enzyme catalysis; methyl-coenzyme M reductase; post-translational modification