7qbt
From Proteopedia
B12-dependent radical SAM methyltransferase, Mmp10 with [4Fe-4S] cluster, cobalamin, and S-methyl-5'-thioadenosine bound.
Structural highlights
FunctionMCRAM_METAC Radical SAM methyltransferase that is responsible for the C(5)-methylation of 'Arg-285' of the methyl-coenzyme M reductase (MCR) subunit alpha McrA. This post-translational methylation, despite being not essential in vivo, plays a role for the stability and structural integrity of MCR.[1] Publication Abstract from PubMedBy catalysing the microbial formation of methane, methyl-coenzyme M reductase has a central role in the global levels of this greenhouse gas(1,2). The activity of methyl-coenzyme M reductase is profoundly affected by several unique post-translational modifications(3-6), such as a unique C-methylation reaction catalysed by methanogenesis marker protein 10 (Mmp10), a radical S-adenosyl-L-methionine (SAM) enzyme(7,8). Here we report the spectroscopic investigation and atomic resolution structure of Mmp10 from Methanosarcina acetivorans, a unique B12 (cobalamin)-dependent radical SAM enzyme(9). 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. Crystallographic snapshots of a B12-dependent radical SAM methyltransferase.,Fyfe CD, Bernardo-Garcia N, Fradale L, Grimaldi S, Guillot A, Brewee C, Chavas LMG, Legrand P, Benjdia A, Berteau O Nature. 2022 Feb;602(7896):336-342. doi: 10.1038/s41586-021-04355-9. Epub 2022, Feb 2. PMID:35110733[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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