The motor domain determines the large step of myosin-V.
Class-V myosin proceeds along actin filaments with large ( approximately 36 nm) steps. Myosin-V has two heads, each of which consists of a motor domain and a long (23 nm) neck domain. In accordance with the widely accepted lever-arm model, it was suggested that myosin-V steps to successive (36 nm) target zones along the actin helical repeat by tilting its long neck (lever-arm). To test this hypothesis, we measured the mechanical properties of single molecules of myosin-V truncation mutants with neck domains only one-sixth of the native length. Our results show that the processivity and step distance along actin are both similar to those of full-length myosin-V. Thus, the long neck domain is not essential for either the large steps or processivity of myosin-V. These results challenge the lever-arm model. We propose that the motor domain and/or the actomyosin interface enable myosin-V to produce large processive steps during translocation along actin.
Tanaka
Hiroto
H
Single Molecule Processes Project, ICORP, JST, 2-4-14, Senba-higashi, Mino, Osaka 562-0035, Japan.
Homma
Kazuaki
K
Iwane
Atsuko Hikikoshi
AH
Katayama
Eisaku
E
Ikebe
Reiko
R
Saito
Junya
J
Yanagida
Toshio
T
Ikebe
Mitsuo
M
D000199:Actins / Q000502:physiology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001696:Biomechanical Phenomena; D002645:Chickens; D004926:Escherichia coli; D008954:Models, Biological; D020409:Molecular Motor Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D009154:Mutation; D024701:Myosin Type V / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics; D014981:Xenopus
D000199:Actins; D020409:Molecular Motor Proteins; D011993:Recombinant Fusion Proteins; D000255:Adenosine Triphosphate; D024701:Myosin Type V