Methyltransferase that can methylate proteins and, to a lower extent, arsenic (PubMed:18539146, PubMed:21193388, PubMed:30017583, PubMed:31061526, PubMed:31636962). Catalytic subunit of a heterodimer with TRMT112, which monomethylates 'Lys-12' of histone H4 (H4K12me1), a modification present at the promoters of numerous genes encoding cell cycle regulators (PubMed:31061526). Catalytic subunit of a heterodimer with TRMT112, which catalyzes N5-methylation of Glu residue of proteins with a Gly-Gln-Xaa-Xaa-Xaa-Arg motif (PubMed:18539146, PubMed:31632689, PubMed:31636962). Methylates ETF1 on 'Gln-185'; ETF1 needs to be complexed to ERF3 in its GTP-bound form to be efficiently methylated (PubMed:18539146, PubMed:20606008, PubMed:31061526, PubMed:31636962). May also play a role in the modulation of arsenic-induced toxicity by mediating the conversion of monomethylarsonous acid (3+) into the less toxic dimethylarsonic acid (PubMed:21193388, PubMed:25997655). It however only plays a limited role in arsenic metabolism compared with AS3MT (PubMed:25997655). {ECO:0000269|PubMed:18539146, ECO:0000269|PubMed:20606008, ECO:0000269|PubMed:21193388, ECO:0000269|PubMed:25997655, ECO:0000269|PubMed:30017583, ECO:0000269|PubMed:31061526, ECO:0000269|PubMed:31632689, ECO:0000269|PubMed:31636962}. This is the function of HEMK2 (HemK methyltransferase 2, ETF1 glutamine and histone H4 lysine, ENSG00000156239).