Transmission of force and displacement within the myosin molecule.
Myosin is a repetitive impeller of actin, using its catalysis of ATP hydrolysis to derive repeatedly the required free energy decrements. In each impulsion, changes at the myosin active site are transmitted through a series of structural elements to the myosin propeller (lever arm), almost 5 nm away. While the nature of transmission through most elements is evident, that through the so-called converter is not. To investigate how the converter changes linear displacement into rotation, we tested (one at a time) the effect of two Phe residue mutations (at 721 and 775) in the converter on the overall function of a heavy meromyosin (or subfragment 1) system, after first showing by observing kinetic behaviors that neither mutation affects other elements in the transmission. Using three tests (direct movement of the lever arm, activity in a motility assay with actin filaments, and direct force measurement of lever arm function), we found that these mutations affected only movements of the converter and the lever arm. From interpreting our observations in terms of the structure of the converter, we deduce that the linear-rotational transformation in the converter is mediated by a little machine (two Phe residues linked to a Gly) within a machine.
Ohki
Takashi
T
Department of Structural Analysis, National Cardiovascular Center Research Institute, Fujishiro-dai, Suita, Osaka 565-8565, Japan.
Mikhailenko
Sergey V
SV
Morales
Manuel F
MF
Onishi
Hirofumi
H
Mochizuki
Naoki
N
D000255:Adenosine Triphosphate / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002645:Chickens; D005822:Genetic Vectors; D006868:Hydrolysis; D007700:Kinetics; D021962:Membrane Microdomains / Q000201:enzymology / Q000235:genetics; D008956:Models, Chemical; D008958:Models, Molecular; D020409:Molecular Motor Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D009119:Muscle Contraction / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D018995:Myosin Heavy Chains / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D015879:Myosin Subfragments / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D011485:Protein Binding / Q000235:genetics; D017433:Protein Structure, Secondary / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D024745:Smooth Muscle Myosins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D013329:Structure-Activity Relationship
D020409:Molecular Motor Proteins; D015879:Myosin Subfragments; D000255:Adenosine Triphosphate; D024745:Smooth Muscle Myosins; D018995:Myosin Heavy Chains