Protein-histidine N-methyltransferase that specifically mediates 3-methylhistidine (tele-methylhistidine) methylation of actin at 'His-73'. Does not have protein-lysine N-methyltransferase activity and probably only catalyzes histidine methylation of actin. L-histidyl-[protein] + S-adenosyl-L-methionine = H(+) + N(tele)-methyl-L-histidyl-[protein] + S-adenosyl-L-homocysteine The SET domain specifically recognizes and binds actin, suggesting that it does not accommodate substrates diverging from actin. Belongs to the class V-like SAM-binding methyltransferase superfamily. SETD3 actin-histidine methyltransferase family. Was initially reported to have histone methyltransferase activity and methylate 'Lys-36' of histone H3 (H3K36me) (PubMed:21307598). However, this conclusion was based on mass spectrometry data wherin mass shifts were inconsistent with a bona fide methylation event and the histone methyltransferase activity could not be confirmed (By similarity).