ID   MCRA_METTE              Reviewed;          15 AA.
AC   P22948;
DT   01-AUG-1991, integrated into UniProtKB/Swiss-Prot.
DT   01-AUG-1991, sequence version 1.
DT   02-SEP-2026, entry version 56.
DE   RecName: Full=Methyl-coenzyme M reductase subunit alpha;
DE            EC=2.8.4.1 {ECO:0000269|PubMed:2013570};
DE   AltName: Full=Coenzyme-B sulfoethylthiotransferase alpha;
DE   Flags: Fragment;
OS   Methanosarcina thermophila.
OC   Archaea; Methanobacteriati; Methanobacteriota; Stenosarchaea group;
OC   Methanomicrobia; Methanosarcinales; Methanosarcinaceae; Methanosarcina.
OX   NCBI_TaxID=2210;
RN   [1]
RP   PROTEIN SEQUENCE, FUNCTION, CATALYTIC ACTIVITY, COFACTOR,
RP   BIOPHYSICOCHEMICAL PROPERTIES, SUBUNIT, AND SUBCELLULAR LOCATION.
RC   STRAIN=ATCC 43570 / DSM 1825 / OCM 12 / TM-1;
RX   PubMed=2013570; DOI=10.1128/jb.173.8.2481-2487.1991;
RA   Jablonski P.E., Ferry J.G.;
RT   "Purification and properties of methyl coenzyme M methylreductase from
RT   acetate-grown Methanosarcina thermophila.";
RL   J. Bacteriol. 173:2481-2487(1991).
CC   -!- FUNCTION: Component of the methyl-coenzyme M reductase (MCR) I that
CC       catalyzes the reductive cleavage of methyl-coenzyme M (CoM-S-CH3 or 2-
CC       (methylthio)ethanesulfonate) using coenzyme B (CoB or 7-
CC       mercaptoheptanoylthreonine phosphate) as reductant which results in the
CC       production of methane and the mixed heterodisulfide of CoB and CoM
CC       (CoM-S-S-CoB). This is the final step in methanogenesis.
CC       {ECO:0000269|PubMed:2013570}.
CC   -!- CATALYTIC ACTIVITY:
CC       Reaction=coenzyme B + methyl-coenzyme M = methane + coenzyme M-coenzyme
CC         B heterodisulfide; Xref=Rhea:RHEA:12532, ChEBI:CHEBI:16183,
CC         ChEBI:CHEBI:58286, ChEBI:CHEBI:58411, ChEBI:CHEBI:58596; EC=2.8.4.1;
CC         Evidence={ECO:0000269|PubMed:2013570};
CC       PhysiologicalDirection=left-to-right; Xref=Rhea:RHEA:12533;
CC         Evidence={ECO:0000305|PubMed:2013570};
CC   -!- COFACTOR:
CC       Name=coenzyme F430; Xref=ChEBI:CHEBI:60540;
CC         Evidence={ECO:0000269|PubMed:2013570};
CC       Note=Binds 1 coenzyme F430 non-covalently per MCR heterotrimeric
CC       complex. Coenzyme F430 is a yellow nickel porphinoid. Methyl-coenzyme-M
CC       reductase is activated when the enzyme-bound coenzyme F430 is reduced,
CC       probably to the Ni(I) oxidation state. {ECO:0000269|PubMed:2013570};
CC   -!- BIOPHYSICOCHEMICAL PROPERTIES:
CC       Kinetic parameters:
CC         KM=3.3 mM for methyl-coenzyme M {ECO:0000269|PubMed:2013570};
CC         KM=59 uM for coenzyme B {ECO:0000269|PubMed:2013570};
CC         Vmax=125 nmol/min/mg enzyme towards coenzyme B
CC         {ECO:0000269|PubMed:2013570};
CC       pH dependence:
CC         Optimum pH is 7.0. {ECO:0000269|PubMed:2013570};
CC       Temperature dependence:
CC         Optimum temperature is 60 degrees Celsius.
CC         {ECO:0000269|PubMed:2013570};
CC   -!- PATHWAY: One-carbon metabolism; methyl-coenzyme M reduction; methane
CC       from methyl-coenzyme M: step 1/1. {ECO:0000305|PubMed:2013570}.
CC   -!- SUBUNIT: MCR from M.thermophila is a heterotrimer composed of an alpha,
CC       a beta, and a gamma subunit. {ECO:0000269|PubMed:2013570}.
CC   -!- SUBCELLULAR LOCATION: Cytoplasm {ECO:0000305|PubMed:2013570}.
CC   -!- SIMILARITY: Belongs to the methyl-coenzyme M reductase alpha subunit
CC       family. {ECO:0000305}.
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DR   UniPathway; UPA00646; UER00699.
DR   GO; GO:0005737; C:cytoplasm; IEA:UniProtKB-SubCell.
DR   GO; GO:0050524; F:coenzyme-B sulfoethylthiotransferase activity; EXP:UniProtKB.
PE   1: Evidence at protein level;
KW   Cytoplasm; Direct protein sequencing; Methanogenesis; Nickel; Transferase.
FT   CHAIN           1..>15
FT                   /note="Methyl-coenzyme M reductase subunit alpha"
FT                   /id="PRO_0000147459"
FT   NON_TER         15
SQ   SEQUENCE   15 AA;  1686 MW;  D5D59892FCA5F63C CRC64;
     AADIFAKFKT SMEVK
//