Substrate regulation of the sarcoplasmic reticulum ATPase. Transient kinetic studies.
نویسندگان
چکیده
منابع مشابه
Substrate Regulation of the Sarcoplasmic Reticulum ATPase
The rate of phosphorylation of the Ca2+-dependent ATPase of sarcoplasmic reticulum vesicles by ITP and ATP was studied using a millisecond mixing and quenching device. The rate of phosphorylation was slower when the vesicles were preincubated in a Ca2+free medium than when preincubated with Ca’+, regardless of the substrate used and of the pH of the medium. When the vesicles were preincubated w...
متن کاملSubstrate Regulation of Calcium Binding in Ca -ATPase Molecules of the Sarcoplasmic Reticulum
To examine the effect of CTP, GTP, ITP, and UTP on calcium binding of Ca -ATPase molecules of the sarcoplasmic reticulum, the calcium dependence of the Ca activated hydrolysis activities of these NTPs of the enzyme molecules was examined by comparison with that of calcium binding of the molecules in the absence of the NTPs at pH 7.40. In the sarcoplasmic reticulum membrane, CTP, GTP, and ITP di...
متن کاملEquilibrium and kinetic studies of calcium transport and ATPase activity in sarcoplasmic reticulum.
A number of equilibrium and kinetic measurements are presented to characterize the partial reactions of the ATPase and transport cycle in sarcoplasmic reticulum vesicles. The cycle begins with calcium and nucleotide binding on sites available on the outer surface of the vesicles. A phosphorylated enzyme intermediate is then formed, and the calcium sites are subjected to a change in their orient...
متن کاملTwo alternate kinetic routes for the decomposition of the phosphorylated intermediate of sarcoplasmic reticulum Ca2+-ATPase.
The decomposition of the phosphorylated intermediate (EP) of sarcoplasmic reticulum ATPase, purified by the method of deoxycholic acid extraction, was studied by first phosphorylating with [gamma-32P]ATP, then diluting the reaction mixture with 20 volumes of medium containing nonradioactive ATP, and finally quenching serial samples with acid for determination of residual [32P]EP. The time cours...
متن کاملReaction mechanism of Ca2+ ATPase of sarcoplasmic reticulum. Equilibrium and transient study of phosphorylation with Ca.ATP as substrate.
At pH 7.0 and 5 degrees C, in the absence of potassium and magnesium, the Ca-ATPase of the sarcoplasmic reticulum slowly hydrolyzes the Ca.ATP at a rate of 0.05 s-1. During turnover 4 nmol of phosphoenzyme per mg of total protein accumulate with a Km value of 10(-8) M. Combining rapid filtration and rapid acid quenching, we took advantage of the above properties to study the early steps of phos...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Journal of Biological Chemistry
سال: 1979
ISSN: 0021-9258
DOI: 10.1016/s0021-9258(19)86697-8