Fig. 1: MCR and Mmp10 activity with overall structure of Mmp10.

a, The activity of MCR producing CoB–CoM heterodisulfide and methane is enhanced by the post-translational modification of R285 catalysed by the B₁₂-dependent radical SAM enzyme Mmp10. b, Overall structure of Mmp10 with bound sodium, [4Fe–4S] cluster, MTA, MeCbl and single iron atom cofactors (Protein Data Bank (PDB) accession 7QBT). Although Mmp10 was crystallized with SAM, only electron density for MTA was observed (Extended Data Fig. 1, Extended Data Table 1). c, Magnified view of the [4Fe–4S] cluster coordinated by three cysteine residues and Y115 alongside the modelled MTA molecule not coordinated to the cluster (Extended Data Fig. 1b). d, Iron loop with a single iron atom coordinated by four cysteine residues (Extended Data Fig. 1c). Light blue, radical SAM domain; teal, cobalamin-binding domain; purple, iron loop; green, MTA; magenta, MeCbl. The [4Fe–4S] cluster is shown as yellow and orange spheres; the single iron is presented as an orange sphere; and the sodium atom is shown as a violet sphere. Omit maps (blue mesh) of the [4Fe–4S] cluster, its coordinated Y115 and the uncoordinated MTA (c) or single iron atom (d) contoured at 3σ are depicted.