A STRUCTURAL ORIGIN OF LATENCY RELAXATION IN FROG SKELETAL MUSCLE
Naoto Yagi 1*
1 JASRI, SPring-8
* To whom correspondence should be addressed. E-mail: yagi{at}spring8.or.jp.
Submitted on June 7, 2006
Revised on July 14, 2006
Accepted on 6 September 2006
 |
Abstract |
|---|
A time-resolved X-ray diffraction study at a time resolution of 0.53 msec was made to investigate the structural origin of latency relaxation in frog skeletal muscle. Intensity and spacing measurements were made on meridional reflections from the Ca-binding protein troponin and the thick filament, and on layer-lines from the thin filament. At 16 °C, the intensity and spacing of all reflections started to change at 4 msec, simultaneously with the latency relaxation. At 0 °C, the intensity of the troponin reflection and the layer lines from the thin filament, and the spacing of the 14.3-nm myosin meridional reflection, but not the spacing of other myosin meridional reflections, began to change at around 15 msec, when the latency relaxation also started. Intensity of myosin-based reflections started to change later. When the muscle was stretched to non-overlap length, the intensity and spacing changes of the myosin reflections disappeared. The simultaneous spacing change of the 14.3-nm myosin meridional reflection with the latency relaxation suggests that detachment of myosin heads that are bound to actin in the resting muscle is the cause of the latency relaxation.
Key Words:
latency relaxation, myosin cross-bridge, synchrotron radiation, x-ray diffraction
