کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5372310 | 1503983 | 2007 | 7 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Temperature dependence of binding and catalysis for the Cdc25B phosphatase
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی تئوریک و عملی
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چکیده انگلیسی
Using a combination of steady-state and single-turnover kinetics, we probe the temperature dependence of substrate association and chemistry for the reaction of Cdc25B phosphatase with its Cdk2-pTpY/CycA protein substrate. The transition state for substrate association is dominated by an enthalpic barrier (ÎHâ¡ of 13 kcal/mol) and has a favorable entropic contribution of 4 kcal/mol at 298 K. Phosphate transfer from Cdk2-pTpY/CycA to enzyme (ÎHâ¡ of 12 kcal/mol) is enthalpically more favorable than for the small molecule substrate p-nitrophenyl phosphate (ÎHâ¡ of 18 kcal/mol), yet entropically less favorable (TÎSâ¡ of 2 vs. â 6 kcal/mol at 298 K, respectively). By measuring the temperature dependence of binding and catalysis for several hotspot mutants involved in binding of protein substrate, we determine the enthalpy-entropy compensations for changes in rates of association and phosphate transfer compared to the wild type system. We conclude that the transition state for enzyme-substrate association involves tight and specific contacts at the remote docking site and that phospho-transfer from Cdk2-pTpY/CycA to the pre-organized active site of the enzyme is accompanied by unfavorable entropic rearrangements that promote rapid product dissociation.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Biophysical Chemistry - Volume 125, Issues 2â3, February 2007, Pages 549-555
Journal: Biophysical Chemistry - Volume 125, Issues 2â3, February 2007, Pages 549-555
نویسندگان
Jungsan Sohn, Johannes Rudolph,