Inhibitory Ca(2+)-regulation of myosin light chain kinase in the lower eukaryote, Physarum polycephalum: role of a Ca(2+)-dependent inhibitory factor
| Autor: | T, Okagaki, R, Ishikawa, K, Kohama |
|---|---|
| Rok vydání: | 1991 |
| Předmět: |
Indoles
Phosphotransferases Carbazoles Protozoan Proteins Models Biological Indole Alkaloids Enzyme Activation Spectrometry Fluorescence Calmodulin Physarum polycephalum Calcium-Calmodulin-Dependent Protein Kinases Animals Calcium Phosphorylation Myosin-Light-Chain Kinase Protein Kinase Inhibitors Protein Kinases |
| Zdroj: | European journal of cell biology. 56(1) |
| ISSN: | 0171-9335 |
| Popis: | ATP-dependent interactions between myosin and actin in the lower eukaryote, Physarum polycephalum, are inhibited by micromolar levels of Ca2+. This inhibition is mediated by the binding of Ca2+ to myosin, the phosphorylation of which is required if Ca2+ is to inhibit the activities of myosin (Kohama, K., Trends Pharmacol. Sci. 11, 433-435 (1990)). As the first step to examine whether Ca2+ also regulates phosphorylation in the actomyosin system, we purified myosin light chain kinase (MLCK) of 55 kDa almost to homogeneity. The MLCK activity was high whether or not Ca2+ was present. However, a Ca(2+)-dependent inhibitory factor (CIF) purified from Physarum (Okagaki et al., Biochem. Biophys. Res. Commun. 176, 564-570 (1991)) was shown to reduce the MLCK activity in a Ca(2+)-dependent manner. Using crude preparations, not only MLCK but also myosin heavy chain kinase and actin kinase were shown to be inhibited by Ca2+ half-maximally at micromolar levels. Since CIF is the only Ca(2+)-binding protein in the preparations, we propose that this inhibitory Ca(2+)-regulation of the kinases for actomyosin is mediated by CIF. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|