Evidence that myosin light chain phosphorylation regulates contraction in the body wall muscles of the sea cucumber
✍ Scribed by W. G. L. Kerrick; L. L. Bolles
- Publisher
- John Wiley and Sons
- Year
- 1982
- Tongue
- English
- Weight
- 931 KB
- Volume
- 112
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
Abstract
The Ca^2+^ activation mechanism of the longitudinal body wall muscles of Parastichopus californicus (sea cucumber) was studied using skinned muscle fiber bundles. Reversible phosphorylation of the myosin light chains correlated with Ca^2+^‐activated tension and relaxation. Pretreatment of the skinned fibers with ATPγS and high Ca^2+^ (10^‐5^M) resulted in irreversible thiophosphorylation of the myosin light chains and activation of a Ca^2+^ insensitive tension. In contrast, pretreatment with low Ca^2+^ (10^‐8^M) and ATPγS results in no thiophosphorylation of the myosin light chains or irreversible activation of tension. These results are consistent with a Ca^2+^‐sensitive myosin light chain kinase/phosphatase system being responsible for the activation of the muscle. Other agents known to have an effect upon the Ca^2+^‐activated tension in skinned vertebrate smooth muscle fibers (trifluoperazine, catalytic subunit of the cyclic AMP‐dependent protein kinase, and calmodulin) did not have an effect on myosin light chain phosphorylation or Ca^2+^‐activated tension. These results suggest a different type of myosin light chain kinase than is found in vertebrate smooth muscle is responsible for the activation of parastichopus longitudinal body wall muscle.