Mechanical and structural properties underlying contraction of skeletal muscle fibers after partial 1-ethyl-3-[3-dimethylamino)propyl]carbodiimide cross-linking.
We show prolonged contraction of permeabilized muscle fibers of the frog during which structural order, as judged from low-angle x-ray diffraction, was preserved by means of partial cross-linking of the fibers using the zero-length cross-linker 1-ethyl-3-[3-dimethylamino)propyl]carbodiimide. Ten to twenty percent of the myosin cross-bridges were cross-linked, allowing the remaining 80-90% to cycle and generate force. These fibers displayed a well-preserved sarcomeric order and mechanical characteristics similar to those of intact muscle fibers. The intensity of the brightest meridional reflection at 14.5 nm, resulting from the projection of cross-bridges evenly spaced along the myofilament length, decreased by 60% as a relaxed fiber was deprived of ATP and entered the rigor state. Upon activation of a rigorized fiber by the addition of ATP, the intensity of this reflection returned to 97% of the relaxed value, suggesting that the overall orientation of cross-bridges in the active muscle was more perpendicular to the filament axis than in rigor. Following a small-amplitude length step applied to the active fibers, the reflection intensity decreased for both releases and stretches. In rigor, however, a small stretch increased the amplitude of the reflection by 35%. These findings show the close link between cross-bridge orientation and tension changes.
Bershitsky
S
S
Institute of Physiology, Russian Academy of Sciences, Yekaterinburg, Russia.
Tsaturyan
A
A
Bershitskaya
O
O
Mashanov
G
G
Brown
P
P
Webb
M
M
Ferenczi
M A
MA
D000199:Actins / Q000737:chemistry; D000818:Animals; D001696:Biomechanical Phenomena; D055592:Biophysical Phenomena; D001703:Biophysics; D002645:Chickens; D003402:Creatine Kinase / Q000378:metabolism; D003432:Cross-Linking Reagents; D005022:Ethyldimethylaminopropyl Carbodiimide; D066298:In Vitro Techniques; D015394:Molecular Structure; D009119:Muscle Contraction / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000737:chemistry / Q000502:physiology; D018482:Muscle, Skeletal / Q000737:chemistry / Q000502:physiology*; D009218:Myosins / Q000737:chemistry; D011896:Rana temporaria; D014961:X-Ray Diffraction
D000199:Actins; D003432:Cross-Linking Reagents; D003402:Creatine Kinase; D009218:Myosins; D005022:Ethyldimethylaminopropyl Carbodiimide