ABSTRACT
The proton needed in the first reaction could be provided by a nearby Tyr residue (Fig. 16), which then would be reprotonated by dissociation of CoB-SH. An
alternative route to Ni(II)-CH3 formation can be provided by the homolytic cleavage of the methyl-CoM bond. This route requires the formation of a thiyl radical on CoB (CoB-S’ ) by the action of an unknown oxidant group present in the cavity and pro posed to be the modified thioglycine Glya445[60]. This radical would react with CH3-SCoM to yield CoM-S-(CH3)-S’ -CoB. The latter would transfer a CH3 radical to Ni(I)- F430, generating the heterodisulfide and CH3-Ni(II)-F430 [60].
