Protein-histidine N-methyltransferase that specifically mediates 3-methylhistidine (tele-methylhistidine) methylation of actin at 'His-73'. Histidine methylation of actin is required for smooth muscle contraction of the laboring uterus during delivery. Does not have protein-lysine N-methyltransferase activity and probably only catalyzes histidine methylation of actin