The mechanism of myosin VI translocation and its load-induced anchoring.
Myosin VI is thought to function as both a transporter and an anchor. While in vitro studies suggest possible mechanisms for processive stepping, a biochemical basis for anchoring has not been demonstrated. Using optical trapping, we observed myosin VI stepping against applied forces. Step size is not strongly affected by such loads. At saturating ATP, myosin VI kinetics shows little dependence on load until, at forces near stall, its stepping slows dramatically as load increases. At subsaturating ATP or in the presence of ADP, stepping kinetics is significantly inhibited by load. From our results, we propose a mechanism of myosin VI stepping that predicts a regulation through load of the motor's roles as transporter and anchor.
Department of Physics, Stanford University, Stanford, CA 94305, USA.
David
D
Altman
H Lee
HL
Sweeney
James A
JA
Spudich
D000199:Actins / Q000378:metabolism; D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001696:Biomechanical Phenomena; D008958:Models, Molecular; D020409:Molecular Motor Proteins / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000378:metabolism*; D011487:Protein Conformation; D021381:Protein Transport; D013314:Stress, Mechanical; D013552:Swine; D013997:Time Factors; D022161:Transport Vesicles / Q000378:metabolism
D000199:Actins; D020409:Molecular Motor Proteins; C089785:myosin VI; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D018995:Myosin Heavy Chains