The nickel enzyme methyl-coenzyme M reductase from methanogenic archaea: In vitro induction of the nickel-based MCR-ox EPR signals from MCR-red2.
Methyl-coenzyme M reductase (MCR) is a nickel enzyme catalyzing the formation of methane from methyl-coenzyme M and coenzyme B in all methanogenic archaea. The active purified enzyme exhibits the axial EPR signal MCR-red1 and in the presence of coenzyme M and coenzyme B the rhombic signal MCR-red2, both derived from Ni(I). Two other EPR-detectable states of the enzyme have been observed in vivo and in vitro designated MCR-ox1 and MCR-ox2 which have quite different nickel EPR signals and which are inactive. Until now the MCR-ox1 and MCR-ox2 states could only be induced in vivo. We report here that in vitro the MCR-red2 state is converted into the MCR-ox1 state by the addition of polysulfide and into a light-sensitive MCR-ox2 state by the addition of sulfite. In the presence of O(2) the MCR-red2 state was converted into a novel third state designated MCR-ox3 and exhibiting two EPR signals similar but not identical to MCR-ox1 and MCR-ox2. The formation of the MCR-ox states was dependent on the presence of coenzyme B. Investigations with the coenzyme B analogues S-methyl-coenzyme B and desulfa-methyl-coenzyme B indicate that for the induction of the MCR-ox states the thiol group of coenzyme B is probably not of importance. The results were obtained with purified active methyl-coenzyme M reductase isoenzyme I from Methanothermobacter marburgensis. They are discussed with respect to the nickel oxidation states in MCR-ox1, MCR-ox2 and MCR-ox3 and to a possible presence of a second redox active group in the active site. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00775-001-0325-z.
Mahlert
Felix
F
Max-Planck-Institut für terrestrische Mikrobiologie and Laboratorium für Mikrobiologie, Fachbereich Biologie, Philipps-Universität, Karl-von-Frisch-Strasse, 35043 Marburg, Germany.
Bauer
Carsten
C
Jaun
Bernhard
B
Thauer
Rudolf K
RK
Duin
Evert C
EC
D002725:Chloroform / Q000737:chemistry; D019343:Citric Acid / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D019605:Euryarchaeota / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D008027:Light; D008665:Metalloporphyrins / Q000737:chemistry; D009532:Nickel; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism*; D010100:Oxygen / Q000737:chemistry; D010769:Phosphothreonine / Q000031:analogs & derivatives / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D013440:Sulfides / Q000737:chemistry; D013447:Sulfites / Q000737:chemistry
D008665:Metalloporphyrins; D013440:Sulfides; D013447:Sulfites; C419387:titanium citrate; C049349:7-mercaptoheptanoylthreonine phosphate; D010769:Phosphothreonine; D019343:Citric Acid; C023540:factor F430; D009532:Nickel; D002725:Chloroform; C032915:polysulfide; D010088:Oxidoreductases; C021572:methyl coenzyme M reductase; D010100:Oxygen