Abstract
We investigated the mechanism of the Ca2+ sensitivity of cross-bridge transitions that limit the rate of force development in vertebrate skeletal muscle. The rate of force development increases with Ca2+ concentration in the physiological range. We show here that at low concentrations of Ca2+ the rate of force development increases after partial extraction of the 20-kD light chain 2 subunit of myosin, whereas reconstitution with light chain 2 fully restores native sensitivity to Ca2+ in skinned single skeletal fibers. Furthermore, elevated free Mg2+ concentration reduces Ca2+ sensitivity, an effect that is reversed by extraction of the light chain but not by disruption of thin-filament activation by partial removal of troponin C, the Ca2+ binding protein of the thin filament. Our findings indicate that the Ca2+ sensitivity of the rate of force development in vertebrate skeletal muscle is mediated in part by the light chain 2 subunit of the myosin cross-bridge.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 460-468 |
| Number of pages | 9 |
| Journal | Biophysical journal |
| Volume | 63 |
| Issue number | 2 |
| DOIs | |
| State | Published - 1992 |
| Externally published | Yes |
Bibliographical note
Funding Information:This study was supported by a grant from the National Institutes of Health.