Regulation of diiron active site of sMMO through regulatory and reductase components from Methylosinus sporium 5.

Abstract

Methanotrophs are key archaea for the regulation of methane gas (CH4), one of the major sources of greenhouse gas, through the expression of sMMO and pMMO. The structures and functions of sMMO, a bacterial multicomponent monooxygenase (BMM) superfamily, are being widely investigated to understand O2 and C-H activations in diiron active sites, although elucidation of its mechanism needs to overcome various factors. Recent advances through structural and spectroscopic support demonstrate conformational changes by component interactions of regulatory (MMOB) and inhibitory enzymes. In this presentation, the allosteric effects of sMMO will be described based on the structural and spectroscopic studies. The hydroxylation of CH4 is accelerated by the interaction of MMOB, and it induces conformational changes for controlling substrates and product pathways. The structures of whole sequences of MMOR have not yet been reported, although structures of FAD-/NADH-binding domain and ferredoxin domain from NMR studies have been reported. The electronic structure of MMOR is investigated through electron paramagnetic resonance (EPR) studies, since it cannot provide its electronic structure with structural information. The annealing method from MMOR shows that Cys50 is first oxidized when it transfers electrons in the [2Fe-2S]+ domain and a neural form of FAD is a major form of cofactor.