Protein-histidine N-methyltransferase that specifically mediates 3-methylhistidine (tele-methylhistidine) methylation of actin at ‘His-73’ (PubMed:30526847, PubMed:30626964, PubMed:30785395, PubMed:31388018, PubMed:31993215). Histidine methylation of actin is required for smooth muscle contraction of the laboring uterus during delivery (PubMed:30626964). Does not have protein-lysine N-methyltransferase activity and probably only catalyzes histidine methylation of actin (PubMed:30626964, PubMed:30785395, PubMed:31388018).