title: Coenzyme M binds to a [4Fe-4S] cluster in the active site of heterodisulfide reductase as deduced from EPR studies with the [33S]coenzyme M-treated enzyme.
abstract: Heterodisulfide reductase (Hdr) from methanogenic Archaea catalyzes the reversible reduction of the heterodisulfide (CoM-S-S-CoB) of the methanogenic thiol coenzymes, coenzyme M (CoM-SH) and coenzyme B (CoB-SH). Upon reaction of the oxidized enzyme with CoM-SH a unique paramagnetic species is formed, which has been shown to be due to a novel type of [4Fe-4S](3+) cluster. In this work, it was addressed whether CoM-SH is directly attached to this [4Fe-4S] cluster using CoM-(33)SH as substrate and purified Hdr from Methanothermobacter marburgensis and Methanosarcina barkeri. With both enzymes treatment with CoM-(33)SH in the presence of duroquinone as an oxidant resulted in a significant broadening of the electron paramagnetic resonance spectrum as compared to CoM-SH as substrate. The signal broadening resulted from an unresolved anisotropic hyperfine coupling between the (33)S nucleus and the paramagnetic center. The results provide compelling evidence for a direct binding of CoM-SH to the [4Fe-4S] cluster in the active site of the enzyme.
authors.affiliation: Max-Planck-Institut für terrestrische Mikrobiologie, Karl-von-Frisch-Strasse, D-35043 Marburg, Germany. duinedu@auburn.edu
authors.forename: Evert C
authors.initials: EC
authors.lastname: Duin
authors.forename: Carsten
authors.initials: C
authors.lastname: Bauer
authors.forename: Bernhard
authors.initials: B
authors.lastname: Jaun
authors.forename: Reiner
authors.initials: R
authors.lastname: Hedderich
mesh_terms: D001665:Binding Sites; D004578:Electron Spin Resonance Spectroscopy; D007506:Iron-Sulfur Proteins / Q000378:metabolism*; D015080:Mesna / Q000378:metabolism*; D010088:Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity; D013460:Sulfur Isotopes
chemical_list: D007506:Iron-Sulfur Proteins; D013460:Sulfur Isotopes; D010088:Oxidoreductases; C087171:heterodisulfide reductase; D015080:Mesna