Cell cycle regulation of myosin-V by calcium/calmodulin-dependent protein kinase II

Organelle transport by myosin-V is down-regulated during mitosis, presumabl y by myosin-V phosphorylation. We used mass spectrometry phosphopeptide map ping to show that the tall of myosin-V was phosphorylated in mitotic Xenopu s egg extract on a single serine residue localized in the carboxyl-terminal organelle-binding domain. Phosphorylation resulted in the release of the m otor from the organelle. The phosphorylation site matched the consensus seq uence of calcium/calmodulin-dependent protein kinase II (CaMKII), and inhib itors of CaMKII prevented myosin-V release. The modulation of cargo binding by phosphorylation is likely to represent a general mechanism regulating o rganelle transport by myosin-V.