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). L-histidyl-[protein] + S-adenosyl-L-methionine = H(+) + N(tele)-methyl-L-histidyl-[protein] + S-adenosyl-L-homocysteine kcat is 0.65 min(-1) with beta-actin as substrate (PubMed:30526847). kcat is 0.809 min(-1) with beta-actin as substrate (PubMed:30785395). kcat is 0.61 min(-1) with S-adenosyl-L-methionine as substrate (PubMed:30526847). kcat is 0.673 min(-1) with S-adenosyl-L-methionine as substrate (PubMed:30785395). Interacts with MYOD1. Localizes mainly in the cytoplasm. Protein levels peak in S phase and are lowest during M phase (at protein level). The SET domain specifically recognizes and binds actin, suggesting that it does not accommodate substrates diverging from actin. Phosphorylated by GSK3B, which is required for recognition by the SCF(FBXW7) complex and subsequent degradation. Ubiquitinated by the SCF(FBXW7) complex following phosphorylation by GSK3B, leading to its degradation by the proteasome. Shows protein-methionine methyltransferase activity in vitro on an actin mutant with a Met instead of a His residue at position 73. 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-4' and 'Lys-36' of histone H3 (H3K4me and H3K36me) (By similarity). However, this conclusion was based on mass spectrometry data wherin mass shifts were inconsistent with a bona fide methylation event (PubMed:30626964). In vitro, the protein-lysine methyltransferase activity is weak compared to the protein-histidine methyltransferase activity (PubMed:30526847). On versatility - Issue 215 of June 2019