AUTHOR=Zhou Yuzhen , Dorchak Alexandria E., Ragsdale Stephen W.

TITLE=In vivo activation of methyl-coenzyme M reductase by carbon monoxide

JOURNAL=Frontiers in Microbiology

VOLUME=Volume 4 - 2013

YEAR=2013

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2013.00069

DOI=10.3389/fmicb.2013.00069

ISSN=1664-302X

ABSTRACT=<p>Methyl-coenzyme M reductase (MCR) from methanogenic archaea catalyzes the rate-limiting and final step in methane biosynthesis. Using coenzyme B as the two-electron donor, MCR reduces methyl-coenzyme M (CH<sub>3</sub>-SCoM) to methane and the mixed disulfide, CoBS-SCoM. MCR contains an essential redox-active nickel tetrahydrocorphinoid cofactor, Coenzyme F<sub>430</sub>, at its active site. The active form of the enzyme (MCR<sub>red1</sub>) contains Ni(I)-F<sub>430</sub>. Rapid and efficient conversion of MCR to MCR<sub>red1</sub> is important for elucidating the enzymatic mechanism, yet this reduction is difficult because the Ni(I) state is subject to oxidative inactivation. Furthermore, no <italic>in vitro</italic> methods have yet been described to convert Ni(II) forms into MCR<sub>red1</sub>. Since 1991, it has been known that MCR<sub>red1</sub> from <italic>Methanothermobacter marburgensis</italic> can be generated <italic>in vivo</italic> when cells are purged with 100% H<sub>2</sub>. Here we show that purging cells or cell extracts with CO can also activate MCR. The rate of <italic>in vivo</italic> activation by CO is about 15 times faster than by H<sub>2</sub> (130 and 8 min<sup>-1</sup>, respectively) and CO leads to twofold higher MCR<sub>red1</sub> than H<sub>2</sub>. Unlike H<sub>2</sub>-dependent activation, which exhibits a 10-h lag time, there is no lag for CO-dependent activation. Based on cyanide inhibition experiments, carbon monoxide dehydrogenase is required for the CO-dependent activation. Formate, which also is a strong reductant, cannot activate MCR in <italic>M. marburgensis in vivo</italic>.</p>