title: Two sub-states of the red2 state of methyl-coenzyme M reductase revealed by high-field EPR spectroscopy.
abstract: Methyl-coenzyme M reductase (MCR) catalyzes the formation of methane from methyl-coenzyme M and coenzyme B in methanogenic archaea. The enzyme has two structurally interlinked active sites embedded in an alpha(2)beta(2)gamma(2) subunit structure. Each active site has the nickel porphyrinoid F(430) as a prosthetic group. In the active state, F(430) contains the transition metal in the Ni(I) oxidation state. The active enzyme exhibits an axial Ni(I)-based continuous wave (CW) electron paramagnetic resonance (EPR) signal, called red1a in the absence of substrates or red1c in the presence of coenzyme M. Addition of coenzyme B to the MCR-red1 state can partially and reversibly convert it into the MCR-red2 form, which shows a rhombic Ni(I)-based EPR signal (at X-band microwave frequencies of approximately 9.4 GHz). In this report we present evidence from high-field/high-frequency CW EPR spectroscopy (W-band, microwave frequency of approximately 94 GHz) that the red2 state consists of two substates that could not be resolved by EPR spectroscopy at X-band frequencies. At W-band it becomes apparent that upon addition of coenzyme B to MCR in the red1c state, two red2 EPR signals are induced, not one as was previously believed. The first signal is the well-characterized (ortho)rhombic EPR signal, thus far called red2, while the second previously unidentified signal is axial. We have named the two substates MCR-red2r and MCR-red2a after their rhombic and axial signals, respectively.
authors: Laboratorium für Physikalische Chemie, ETH Zürich, Wolfgang-Pauli-Strasse 10, Zurich, Switzerland.
authors: Denise I
authors: DI
authors: Kern
authors: Meike
authors: M
authors: Goenrich
authors: Bernhard
authors: B
authors: Jaun
authors: Rudolf K
authors: RK
authors: Thauer
authors: Jeffrey
authors: J
authors: Harmer
authors: Dariush
authors: D
authors: Hinderberger
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry*; D001665:Binding Sites; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D017013:Methanobacteriaceae / Q000201:enzymology*; D009532:Nickel / Q000737:chemistry*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry*
chemical_list: D019843:Archaeal Proteins; D009532:Nickel; D010088:Oxidoreductases; C021572:methyl coenzyme M reductase
references: J Biol Inorg Chem. 2003 May;8(5):586-93
references: 12624730
references: J Biol Chem. 2006 Nov 10;281(45):34663-76
references: 16966321
references: J Magn Reson. 2006 Jan;178(1):42-55
references: 16188474
references: J Biol Inorg Chem. 2004 Jul;9(5):563-76
references: 15160314
references: J Am Chem Soc. 2003 Apr 30;125(17):4988-9
references: 12708843
references: Eur J Biochem. 1988 Mar 15;172(3):669-77
references: 3350018
references: Eur J Biochem. 1990 Dec 27;194(3):871-7
references: 2269306
references: Biochemistry. 1978 Jun 13;17(12):2374-7
references: 98178
references: Microbiology. 1998 Sep;144 ( Pt 9):2377-406
references: 9782487
references: Bacteriol Rev. 1977 Mar;41(1):100-80
references: 860983
references: Eur J Biochem. 1997 Jan 15;243(1-2):110-4
references: 9030728
references: J Am Chem Soc. 2002 Apr 17;124(15):4039-49
references: 11942842
references: Int J Syst Evol Microbiol. 2000 Jan;50 Pt 1:43-53
references: 10826786
references: Eur J Biochem. 1993 Oct 15;217(2):587-95
references: 8223602
references: J Biol Inorg Chem. 2002 Apr;7(4-5):500-13
references: 11941508
references: J Biol Inorg Chem. 2002 Jan;7(1-2):101-12
references: 11862546
references: Science. 1997 Nov 21;278(5342):1457-62
references: 9367957
references: Anal Biochem. 1976 May 7;72:248-54
references: 942051
references: J Biol Inorg Chem. 2005 Jun;10(4):333-42
references: 15846525