page_title: Myosin
section_title: Myosin V
hierarchical_section_title: Myosin / Nomenclature, evolution, and the family tree / Myosin classes / Myosin V
caption_attribution_description: English: Crystal structure of myosin V motor with essential light chain - nucleotide-free. A structural state of the myosin V motor without bound nucleotide. Visualized with UCSF Chimera. PDB: 1OE9
context_page_description: Myosins are a superfamily of motor proteins best known for their roles in muscle contraction and in a wide range of other motility processes in eukaryotes. They are ATP-dependent and responsible for actin-based motility. The term was originally used to describe a group of similar ATPases found in the cells of both striated muscle tissue and smooth muscle tissue. Following the discovery by Pollard and Korn of enzymes with myosin-like function in Acanthamoeba castellanii, a global range of divergent myosin genes have been discovered throughout the realm of eukaryotes.
  Although myosin was originally thought to be restricted to muscle cells, there is no single "myosin"; rather it is a very large superfamily of genes whose protein products share the basic properties of actin binding, ATP hydrolysis, and force transduction. Virtually all eukaryotic cells contain myosin isoforms. Some isoforms have specialized functions in certain cell types, while other isoforms are ubiquitous. The structure and function of myosin is globally conserved across species, to the extent that rabbit muscle myosin II will bind to actin from an amoeba.
context_section_description: Myosin V is an unconventional myosin motor, which is processive as a dimer and has a step size of 36 nm. It translocates (walks) along actin filaments traveling towards the barbed end (+ end) of the filaments. Myosin V is involved in the transport of cargo (e.g. RNA, vesicles, organelles, mitochondria) from the center of the cell to the periphery, but has been furthermore shown to act like a dynamic tether, retaining vesicles and organelles in the actin-rich periphery of cells. A recent single molecule in vitro reconstitution study on assembling actin filaments suggests that Myosin V travels farther on newly assembling (ADP-Pi rich) F-actin, while processive runlengths are shorter on older (ADP-rich) F-actin.
caption: Crystal structure of myosin V motor with essential light chain – nucleotide-free
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