The tail binds to the head-neck domain, inhibiting ATPase activity of myosin VIIA.
Myosin VIIA is an unconventional myosin, responsible for human Usher syndrome type 1B, which causes hearing and visual loss. Here, we studied the molecular mechanism of regulation of myosin VIIA, which is currently unknown. Although it was originally thought that myosin VIIA is a dimeric myosin, our electron microscopic (EM) observations revealed that full-length Drosophila myosin VIIA (DM7A) is a monomer. Interestingly, the tail domain markedly inhibits the actin-activated ATPase activity of tailless DM7A at low Ca(2+) but not high Ca(2+). By examining various deletion constructs, we found that deletion of the distal IQ domain, the C-terminal region of the tail, and the N-terminal region of the tail abolishes the tail-induced inhibition of ATPase activity. Single-particle EM analysis of full-length DM7A at low Ca(2+) suggests that the tail folds back on to the head, where it contacts both the motor core domain and the neck domain, forming an inhibited conformation. We concluded that unconventional myosin that may be present a monomer in the cell can be regulated by intramolecular interaction of the tail with the head.
Department of Physiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA.
Nobuhisa
N
Umeki
Hyun Suk
HS
Jung
Shinya
S
Watanabe
Tsuyoshi
T
Sakai
Xiang-dong
XD
Li
Reiko
R
Ikebe
Roger
R
Craig
Mitsuo
M
Ikebe
D000818:Animals; D004331:Drosophila melanogaster / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D004398:Dyneins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure; D004789:Enzyme Activation; D009043:Motor Activity; D000081412:Myosin VIIa; D009218:Myosins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure; D011485:Protein Binding
C000631455:MYO7A protein, human; D000081412:Myosin VIIa; C000631458:myosin 7a, Drosophila; D009218:Myosins; D004398:Dyneins