Phosphorylation of myosin regulatory light chain has minimal effect on kinetics and distribution of orientations of cross bridges of rabbit skeletal muscle
| Autor: | Julian Borejdo, Krishna Midde, Ignacy Gryczynski, Rafal Fudala, Janhavi Nagwekar, Divya Duggal, Ryan Rich |
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| Rok vydání: | 2014 |
| Předmět: |
Myofilament
Myosin Light Chains Myosin light-chain kinase Cardiovascular and Renal Integration Physiology macromolecular substances Myosins Myosin head Myofibrils Physiology (medical) Myosin medicine Animals Phosphorylation Muscle Skeletal Actin Meromyosin Chemistry Skeletal muscle Kinetics medicine.anatomical_structure Biochemistry Biophysics Rabbits Myofibril Muscle Contraction |
| Zdroj: | American Journal of Physiology-Regulatory, Integrative and Comparative Physiology. 306:R222-R233 |
| ISSN: | 1522-1490 0363-6119 |
| Popis: | Force production in muscle results from ATP-driven cyclic interactions of myosin with actin. A myosin cross bridge consists of a globular head domain, containing actin and ATP-binding sites, and a neck domain with the associated light chain 1 (LC1) and the regulatory light chain (RLC). The actin polymer serves as a “rail” over which myosin translates. Phosphorylation of the RLC is thought to play a significant role in the regulation of muscle relaxation by increasing the degree of skeletal cross-bridge disorder and increasing muscle ATPase activity. The effect of phosphorylation on skeletal cross-bridge kinetics and the distribution of orientations during steady-state contraction of rabbit muscle is investigated here. Because the kinetics and orientation of an assembly of cross bridges (XBs) can only be studied when an individual XB makes a significant contribution to the overall signal, the number of observed XBs was minimized to ∼20 by limiting the detection volume and concentration of fluorescent XBs. The autofluorescence and photobleaching from an ex vivo sample was reduced by choosing a dye that was excited in the red and observed in the far red. The interference from scattering was eliminated by gating the signal. These techniques decrease large uncertainties associated with determination of the effect of phosphorylation on a few molecules ex vivo with millisecond time resolution. In spite of the remaining uncertainties, we conclude that the state of phosphorylation of RLC had no effect on the rate of dissociation of cross bridges from thin filaments, on the rate of myosin head binding to thin filaments, and on the rate of power stroke. On the other hand, phosphorylation slightly increased the degree of disorder of active cross bridges. |
| Databáze: | OpenAIRE |
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