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Crystallographic snapshots of a B12-dependent radical SAM methyltransferase.


ABSTRACT: By catalysing the microbial formation of methane, methyl-coenzyme M reductase has a central role in the global levels of this greenhouse gas1,2. The activity of methyl-coenzyme M reductase is profoundly affected by several unique post-translational modifications3-6, such as  a unique C-methylation reaction catalysed by methanogenesis marker protein 10 (Mmp10), a radical S-adenosyl-L-methionine (SAM) enzyme7,8. Here we report the spectroscopic investigation and atomic resolution structure of Mmp10 from Methanosarcina acetivorans, a unique B12 (cobalamin)-dependent radical SAM enzyme9. The structure of Mmp10 reveals a unique enzyme architecture with four metallic centres and critical structural features involved in the control of catalysis. In addition, the structure of the enzyme-substrate complex offers a glimpse into a B12-dependent radical SAM enzyme in a precatalytic state. By combining electron paramagnetic resonance spectroscopy, structural biology and biochemistry, our study illuminates the mechanism by which the emerging superfamily of B12-dependent radical SAM enzymes catalyse chemically challenging alkylation reactions and identifies distinctive active site rearrangements to provide a structural rationale for the dual use of the SAM cofactor for radical and nucleophilic chemistry.

SUBMITTER: Fyfe CD 

PROVIDER: S-EPMC8828468 | biostudies-literature | 2022 Feb

REPOSITORIES: biostudies-literature

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By catalysing the microbial formation of methane, methyl-coenzyme M reductase has a central role in the global levels of this greenhouse gas<sup>1,2</sup>. The activity of methyl-coenzyme M reductase is profoundly affected by several unique post-translational modifications<sup>3-6</sup>, such as  a unique C-methylation reaction catalysed by methanogenesis marker protein 10 (Mmp10), a radical S-adenosyl-L-methionine (SAM) enzyme<sup>7,8</sup>. Here we report the spectroscopic investigation and at  ...[more]

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