Methyltransferase involved in methanogenesis in the methanol pathway. Catalyzes the transfer of the methyl group from the methylated corrinoid protein MtaC to coenzyme M, forming the substrate for coenzyme-B sulfoethylthiotransferase. MtaC can be substituted by free cob(I)alamin in vitro. coenzyme M + methyl-Co(III)-[methanol-specific corrinoid protein] = Co(I)-[methanol-specific corrinoid protein] + H(+) + methyl-coenzyme M Zn(2+) is involved in coenzyme M activation: in the absence of coenzyme M, zinc is coordinated by a single sulfur ligand and three oxygen or nitrogen ligands. In the presence of coenzyme M, one oxygen/nitrogen-ligand is replaced by sulfur, probably due to ligation of the thiol group of coenzyme M. Belongs to the uroporphyrinogen decarboxylase family. MtbA/mtaA subfamily.