A myosin II mutation uncouples ATPase activity from motility and shortens step size.
It is thought that Switch II of myosin, kinesin and G proteins has an important function in relating nucleotide state to protein conformation. Here we examine a myosin mutant containing an S456L substitution in the Switch II region. In this protein, mechanical activity is uncoupled from the chemical energy of ATP hydrolysis so that its gliding velocity on actin filaments is only one-tenth of that of the wild type. The mutant spends longer in the strongly bound state and exhibits a shorter step size, which together account for the reduction in in vitro velocity. This is the first single point mutation in myosin that has been found to affect step size.
Departments of Biochemistry and Developmental Biology, Stanford University School of Medicine, Stanford, California 94305, USA.
C T
CT
Murphy
R S
RS
Rock
J A
JA
Spudich
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D020134:Catalytic Domain; D004023:Dictyostelium / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D007700:Kinetics; D008954:Models, Biological; D008958:Models, Molecular; D020409:Molecular Motor Proteins / Q000378:metabolism; D009068:Movement; D009154:Mutation; D009218:Myosins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D010957:Plasmids; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D013053:Spectrophotometry; D014170:Transformation, Genetic
D020409:Molecular Motor Proteins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D009218:Myosins