Axial disposition of myosin heads in isometrically contracting muscles.
Meridional x-ray diffraction diagrams, recorded with high angular resolution, from muscles contracting at the plateau of isometric tension show that the myosin diffraction orders are clusters of peaks. These clusters are due to pronounced interference effects between the myosin diffracting units on either side of the M-line. A theoretical analysis based on the polarity of the myosin (and actin) filaments shows that it is possible to extract phase information from which the axial disposition of the myosin heads can be determined. The results show that each head in a crown pair has a distinct structural disposition. It appears that only one of the heads in the pair stereospecifically interacts with the thin filament at any one time.
Laboratori Llum Sincrotró-Institut Física Altes Energies, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Barcelona, Spain.
J
J
Juanhuix
J
J
Bordas
J
J
Campmany
A
A
Svensson
M L
ML
Bassford
T
T
Narayanan
D000199:Actins / Q000737:chemistry / Q000502:physiology; D000818:Animals; D007537:Isometric Contraction / Q000502:physiology*; D008954:Models, Biological; D008958:Models, Molecular; D008962:Models, Theoretical; D018482:Muscle, Skeletal / Q000502:physiology* / Q000648:ultrastructure; D009218:Myosins / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure; D011487:Protein Conformation; D011893:Rana esculenta; D014961:X-Ray Diffraction
D000199:Actins; D009218:Myosins