The function of ENSG00000099331 (MYO9B, myosin IXB) is as follows. Myosins are actin-based motor molecules with ATPase activity. Unconventional myosins serve in intracellular movements. Binds actin with high affinity both in the absence and presence of ATP and its mechanochemical activity is inhibited by calcium ions (PubMed:9490638). Also acts as a GTPase activator for RHOA (PubMed:26529257, PubMed:9490638). Plays a role in the regulation of cell migration via its role as RHOA GTPase activator. This is regulated by its interaction with the SLIT2 receptor ROBO1; interaction with ROBO1 impairs interaction with RHOA and subsequent activation of RHOA GTPase activity, and thereby leads to increased levels of active, GTP-bound RHOA (PubMed:26529257). {ECO:0000269|PubMed:26529257, ECO:0000269|PubMed:9490638}.