Heterologous expression and assembly of methyl‐coenzyme M reductase from anaerobic methanotrophs

Abstract

Methyl-coenzyme M reductase (MCR) is the key rate-determining enzyme of methanogenesis and anaerobic oxidation of methane, the essential energy metabolisms of methanogenic archaea and anaerobic methanotrophs (ANME), respectively. Given the role of methane as both a potent greenhouse gas as well as a valuable energy source, understanding the biochemistry of its production and consumption in nature is becoming increasingly important. Extensive studies on methanogenic MCR have revealed key biochemical and mechanistic insights, however, the catalytic properties of ANME MCR have yet to be reported. This is due to the difficulties associated with culturing ANME organisms in a lab setting, which is hindered by extremely slow growth rates and a characteristic dependence of bacterial partners. MCR is a dimer of heterotrimers with a 2α, 2β, 2γ configuration and requires the unique nickel tetrapyrrole prosthetic group, coenzyme F430, thus rendering MCR a difficult enzyme to be produced using a heterologous expression system. Here we report our progress in the development of such a system for expressing recombinant ANME MCRs in the model methanogen, Methanococcus maripaludis. This work lays the foundation for future biochemical and mechanistic studies of anaerobic C-H bond activation catalyzed by ANME MCR.