Class V myosins are well studied unconventional myosins, represented by three paralogs (Myo5a,b,c) in vertebrates. Their C-terminal cargo binding domains (CBDs) are important for the binding of a diverse set of cargos, including membrane vesicles, organelles, proteins and mRNA. They interact with several adaptor proteins, in case of Myo5a-CBD, melanophilin (MLPH), Rab interacting lysosomal protein-like 2 (RILPL2), and granuphilin []. Mutations in human Myo5a (many of which map to the cargo binding domain) lead to Griscelli syndrome, a severe neurological disease [].
Class V myosins have been shown to play a role in both membrane trafficking and RNA transport []. There are two type V myosins in yeast, which appear to have nonoverlapping functions. In Schizosaccharomyces pombe Myo52 is involved in growth polarity and cytokinesis, whereas Myo51 is a component of the cytokinetic actin ring []. Similarly, Saccharomyces cerevisiae Myo2 is essential for polarized growth, most likely through transport of secretory vesicles to the developing bud [], while Myo4 has been proposed to transport a mRNA needed to repress mating type switching in daughter cells []. Mice and humans possess three class V myosins (Myo5A, Myo5B, and Myo5C). Possible cargoes for myosin-V in mammals include melanosomes, synaptic vesicles [, , ]and organelles in neurons []. Mutations in myo5A cause Griscelli syndrome type-1 (GS1) and neuroectodermal melanolysosomal disease, or Elejalde disease [].This entry represents the motor (head) domain of class V myosins []. The motor domain has ATPase activity and belongs to the larger group of P-loop NTPases.
