Myosin IXB (MYO9B)

has four IQ motifs located in the neck domain that bind calmodulin, which serves as a light chain. The protein complex has a single-headed structure and exhibits processive movement on actin filaments toward the minus-end. The protein also has rho-GTPase activity. Polymorphisms in this gene are associated with celiac disease and ulcerative colitis susceptibility. Like other myosins, MYO9B contains an N-terminal head or motor domain, a neck domain containing 4 tandemly repeated IQ motifs, and a large C-terminal tail. Compared to conventional myosins, the MYO9B head region contains several unusual insertions and the tail region contains a putative GTPase-activating protein domain and putative binding domains for zinc and diacylglycerol.