PT  - JOURNAL ARTICLE
AU  - Dipti D. Nayak
AU  - Nilkamal Mahanta
AU  - Douglas A. Mitchell
AU  - William W. Metcalf
TI  - Post-translational thioamidation of methyl-coenzyme M reductase, a key enzyme in methanogenic and methanotrophic Archaea
AID  - 10.1101/121111
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 121111
4099  - http://biorxiv.org/content/early/2017/03/27/121111.short
4100  - http://biorxiv.org/content/early/2017/03/27/121111.full
AB  - The enzyme methyl-coenzyme M reductase (MCR), found in strictly anaerobic methanogenic and methanotrophic archaea, catalyzes a reversible reaction involved in the production and consumption of the potent greenhouse gas methane. The α subunit of this enzyme (McrA) contains several unusual post-translational modifications, including an exceptionally rare thioamidation of glycine. Based on the presumed function of homologous genes involved in the biosynthesis of thioamide-containing natural products, we hypothesized that the archaeal tfuA and ycaO genes would be responsible for post-translational installation of thioglycine into McrA. Mass spectrometric characterization of McrA in a ΔycaO-tfuA mutant of the methanogenic archaeon Methanosarcina acetivorans revealed the presence of glycine, rather than thioglycine, supporting this hypothesis. Physiological characterization of this mutant suggested a new role for the thioglycine modification in enhancing protein stability, as opposed to playing a direct catalytic role. The universal conservation of this modification suggests that MCR arose in a thermophilic ancestor.