Myosin IIIB (MYO3B)

Class III myosins are actin-dependent motor proteins that contain amino-terminal kinase domains and are expressed in photoreceptors. Using BLAST analysis with the sequence of MYO3A as query, followed by RACE on human retinal cDNA, Dose and Burnside (2002) cloned a full-length MYO3B cDNA and revealed alternative 3-prime splice variants. Similar to other class III myosins, MYO3B contains an N-terminal kinase domain, followed by motor, neck, and tail domains. The MYO3B gene generates a variety of splice variants that contain 1 or 2 calmodulin-binding (IQ) motifs in the neck domain and 1 of 3 domains in the tail domain. Northern blot analysis showed expression of a 7-kb MYO3B transcript in human retina, but not in an RPE cell line; two 6- and 7-kb MYO3B transcripts in kidney; and a 4-kb transcript in testis.