| Modification Notes |
Myosin XVIIIB (MYO18B) is a 2,567 amino acid, unconventional myosin heavy chain that is expressed mainly in human cardiac and skeletal muscles and, at much lower levels, in the testis. Myosin XVIIIB is located in the cytoplasm of undifferentiated myoblast cells and has an N-terminal head domain functioning as a motor (with an ATP-binding site as well as an actin-binding region), a neck region containing an IQ motif, and a C-terminal tail with a short coiled-coil domain allowing for dimerization to form a 2-headed structure. Sug1, a regulator of the 26S proteasome, binds to the C-terminal tail of Myosin XVIIIB. This Sug1 binding causes an upregulation of Myosin XVIIIB. Myosin XVIIIB is frequently deleted, mutated and/or hypermethylated in lung and ovarian cancers, suggesting its candidacy as a tumor-suppressor. Furthermore, the Histones H3 and H4 play a role in the regulation of Myosin XVIIIB expression, so histone deacetylation surrounding the promoter region may be involved in lung and ovarian carcinomas. |