C-methyltransferase activity protein methyltransferase activity S-adenosylmethionine-dependent methyltransferase activity protein-arginine C-methyltransferase activity https://github.com/geneontology/go-ontology/issues/23704 https://github.com/geneontology/go-ontology/issues/30193 RHEA:66028 peptidyl-arginine C-methylase activity protein-arginine C-methylase activity GO:0035244 peptidyl-arginine C-methyltransferase activity EC:2.1.1.379 peptidyl arginine C-methyltransferase activity Catalysis of the transfer of a methyl group to the carbon atom of an arginine residue in a protein. This modification has been detected in anaerobic bacteria. molecular_function