A Conformational Change in the Junctional Foot Protein Is Involved in the Regulation of Ca2+ Release from Sarcoplasmic Reticulum
| Autor: | Masafumi Yano, Noriaki Ikemoto, Roque El-Hayek |
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| Rok vydání: | 1995 |
| Předmět: | |
| Zdroj: | Journal of Biological Chemistry. 270:15634-15638 |
| ISSN: | 0021-9258 3288-3293 |
| DOI: | 10.1074/jbc.270.26.15634 |
| Popis: | We investigated both conformational changes in the junctional foot protein (JFP) and Ca2+ release from sarcoplasmic reticulum (SR) in parallel after stimulation of triadic vesicles by the JFP-specific ligand, polylysine. To monitor protein conformational change, the JFP was labeled in a site-directed fashion with the fluorescent conformational probe methylcoumarin acetate (MCA) (Kang, J. J., Tarcsafalvi, A., Carlos, A. D., Fujimoto, E., Shahrokh, Z., Thevenin, B. J.-M., Shohet, S. B., and Ikemoto, N.(1992) Biochemistry 31, 3288-3293). The induction of SR Ca2+ release by polylysine produced a rapid increase in the fluorescence intensity of the JFP-bound MCA. The polylysine concentration dependence of the fluorescence change was essentially the same as that of Ca2+ release, suggesting that the two events are tightly coupled. However, the rate constant of MCA fluorescence change was much larger than that of Ca2+ release; i.e. the conformational change preceded Ca2+ release. Prevention of protein conformational change by lysine (0.2 M) inhibited Ca2+ release from SR. Inhibition of Ca2+ release by Mg2+ (5 mM), however, had little effect on the conformational change. These results suggest that binding of polylysine to the JFP produces conformational changes in the protein, which in turn activates the Ca2+ channel, leading to Ca2+ release from the SR. |
| Databáze: | OpenAIRE |
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