These myosins have an N-terminal motor domain, a light-chain binding domain, and a C-terminal GPA/Q-rich domain. There is little known about the function of this myosin class. Two of the earliest members identified in this class are green alga Acetabularia cliftonii, Aclmyo1 and Aclmyo2. They are striking with their short tail of Aclmyo1 of 18 residues and the maximum of 7 IQ motifs in Aclmyo2. It is thought that these myosins are involved in organelle transport and tip growth. The catalytic (head) domain has ATPase activity and belongs to the larger group of P-loop NTPases. Myosins are actin-dependent molecular motors that play important roles in muscle contraction, cell motility, and organelle transport. The head domain is a molecular motor, which utilizes ATP hydrolysis to generate directed movement toward the plus end along actin filaments. A cyclical interaction between myosin and actin provides the driving force. Rates of ATP hydrolysis and consequently the speed of movement along actin filaments vary widely, from about 0.04 micrometer per second for myosin I to 4.5 micrometer per second for myosin II in skeletal muscle. Myosin II moves in discrete steps about 5-10 nm long and generates 1-5 piconewtons of force. Upon ATP binding, the myosin head dissociates from an actin filament. ATP hydrolysis causes the head to pivot and associate with a new actin subunit. The release of Pi causes the head to pivot and move the filament (power stroke). Release of ADP completes the cycle. CyMoBase classifications were used to confirm and identify the myosins in this hierarchy.
Feature 1:ATP binding site [chemical binding site]
Evidence:
Comment:the residues of the P-loop wrap around the triphosphate region of the nucleotide and the N-terminal region forms the binding pocket for the nucleotide
Jiyao W et al.(2023). "The conserved domain database in 2023.",