Li Y, Bevilacqua P C, Mathews D, Turner D H
Department of Chemistry, University of Rochester, New York 14627-0216, USA.
Biochemistry. 1995 Nov 7;34(44):14394-9. doi: 10.1021/bi00044a016.
Association and dissociation rates for the pyrene-(pyr)-labeled oligoribonucleotide substrate pyrCUCU binding to the L-21 ScaI group I ribozyme are reported as a function of temperature. Combined with thermodynamic parameters for binding of pyrCUCU to rGGAGAA, the results allow calculation of the activation and thermodynamic parameters for docking of pyrCUCU into the catalytic core of the ribozyme. The activation enthalpy for docking is 22 kcal/mol, much larger than the approximately 4 kcal/mol expected for a diffusion-controlled process. Thus, docking is not diffusion-controlled. The activation and equilibrium entropies for docking are favorable at 21 and 37 eu, respectively. The results suggest the rate-limiting step and the driving force for docking may involve desolvation of RNA functional groups or of Mg2+ ions.
报告了芘标记的寡核糖核苷酸底物pyrCUCU与L-21 ScaI I类核酶结合和解离的速率与温度的函数关系。结合pyrCUCU与rGGAGAA结合的热力学参数，这些结果使得能够计算pyrCUCU对接至核酶催化核心的活化和热力学参数。对接的活化焓为22千卡/摩尔，远大于扩散控制过程预期的约4千卡/摩尔。因此，对接不是扩散控制的。对接的活化熵和平衡熵分别在21和37熵单位时是有利的。结果表明，对接的限速步骤和驱动力可能涉及RNA官能团或Mg2+离子的去溶剂化。
