Direct interaction of coenzyme M with the active-site Fe-S cluster of heterodisulfide reductase.
Heterodisulfide reductase (HDR) catalyzes the formation of coenzyme M (CoM-SH) and coenzyme B (CoB-SH) by the reversible reduction of the heterodisulfide, CoM-S-S-CoB. This reaction recycles the two thiol coenzymes involved in the final step of microbial methanogenesis. Electron paramagnetic resonance (EPR) and variable-temperature magnetic circular dichroism spectroscopic experiments on oxidized HDR incubated with CoM-SH revealed a S=1/2 [4Fe-4S]3) cluster, the EPR spectrum of which is broadened in the presence of CoM-33SH [Duin, E.C., Madadi-Kahkesh, S., Hedderich, R., Clay, M.D. and Johnson, M.K. (2002) Heterodisulfide reductase from Methanothermobacter marburgensis contains an active-site [4Fe-4S] cluster that is directly involved in mediating heterodisulfide reduction. FEBS Lett. 512, 263-268; Duin, E.C., Bauer, C., Jaun, B. and Hedderich, R. (2003) 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. FEBS Lett. 538, 81-84]. These results provide indirect evidence that the disulfide binds to the iron-sulfur cluster during reduction. We report here direct structural evidence for this interaction from Se X-ray absorption spectroscopic investigation of HDR treated with the selenium analog of coenzyme M (CoM-SeH). Se K edge extended X-ray absorption fine structure confirms a direct interaction of the Se in CoM-SeH-treated HDR with an Fe atom of the Fe-S cluster at an Fe-Se distance of 2.4A.
Shokes
Jacob E
JE
Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, GA 30602-2556, USA.
Duin
Evert C
EC
Bauer
Carsten
C
Jaun
Bernhard
B
Hedderich
Reiner
R
Koch
Jürgen
J
Scott
Robert A
RA
D001665:Binding Sites; D004220:Disulfides / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000378:metabolism; D015080:Mesna / Q000737:chemistry* / Q000378:metabolism; D017014:Methanobacterium / Q000201:enzymology*; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism; D013057:Spectrum Analysis; D014965:X-Rays
D004220:Disulfides; D007506:Iron-Sulfur Proteins; D007501:Iron; D010088:Oxidoreductases; C087171:heterodisulfide reductase; D015080:Mesna