Cooperative effects of Ca2+ and Sr2+ on sarcoplasmic reticulum adenosine triphosphatase |
| |
| Authors: | J A Holguín |
| |
| Institution: | 1. College of Food Science and Engineering, Tianjin University of Science and Technology, Tianjin 300457, China;2. College of Life Sciences, Yantai University, Yantai, Shandong 264005, China;1. Department of Chemistry, Rice University, Houston, TX 77005;2. Department of Biology and Biochemistry, University of Houston, Houston TX 77004;3. College of Chemical Engineering, Sichuan University Science and Engineering, Zigong, Sichuan 643000, PR China |
| |
| Abstract: | The intrinsic fluorescence of purified Ca-ATPase from skeletal sarcoplasmic reticulum was measured in the presence of various concentrations of Ca2+, Sr2+, and Ba2+. Ca2+ and Sr2+ induce positive cooperative fluorescence enhancement, whereas Ba2+ does not change the fluorescence of ATPase. ATP does not seem to modify the kinetic parameters of Ca2+ and Sr2+ binding to ATPase. Nevertheless, p-nitrophenylphosphate hydrolysis, activated by Ca2+ or Sr2+ at various pHs, changes the affinity and the cooperative behavior for both cations and two components appear in the Hill plots. For Ca2+, nH of 1.6 to 3.5 were obtained, and 1.06 to 1.83 for Sr2+; nH changes of the second component seem to be pH dependent. Differences in the ratio between rates of Ca2+ transport and substrate hydrolysis by sarcoplasmic reticulum were found, i.e., two for ATP and one for p-nitrophenylphosphate. For Sr2+ this ratio was one for either ATP or p-nitrophenylphosphate. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
