Protein-histidine N-methyltransferase that specifically catalyzes 1-methylhistidine (pros-methylhistidine) methylation of target proteins (PubMed:33563959, PubMed:34562450). Mediates methylation of proteins with a His-x-His (HxH) motif (where ‘x’ is preferably a small amino acid) (PubMed:33563959). Catalyzes methylation of target proteins such as S100A9, NDUFB3, SLC39A5, SLC39A7, ARMC6 and DNAJB12; 1-methylhistidine modification may affect the binding of zinc and other metals to its target proteins (PubMed:33563959, PubMed:34562450). Constitutes the main methyltransferase for the 1-methylhistidine modification in cell (PubMed:33563959).