Krantz B A, Sosnick T R
Department of Biochemistry and Molecular Biology, University of Chicago, 920 East 58th Street, Chicago, Illinois 60637, USA.
Biochemistry. 2000 Sep 26;39(38):11696-701. doi: 10.1021/bi000792+.
Conflicting results exist regarding whether the folding of mammalian ubiquitin at 25 degrees C is a simple, two-state kinetic process or a more complex, three-state process with a defined kinetic intermediate. We have measured folding rate constants up to about 1000 s(-1) using conventional rapid mixing methods in single-jump, double-jump, and continuous-flow modes. The linear dependence of folding rates on denaturant concentration and the lack of an unaccounted "burst-phase" change for the fluorescence signal indicate that a two-state folding model is adequate to describe the folding pathway. This behavior also is seen for folding in the presence of the stabilizing additives 0.23 M sodium sulfate and 1 M sodium chloride. These results stress the need for caution in interpreting deviations from ideal two-state "chevron" behavior when folding is heterogeneous or folding rate constants are near the detection limit.
关于哺乳动物泛素在25摄氏度下的折叠是一个简单的两态动力学过程，还是一个更复杂的具有明确动力学中间体的三态过程，存在相互矛盾的结果。我们使用传统的快速混合方法，在单跳、双跳和连续流动模式下测量了高达约1000 s⁻¹ 的折叠速率常数。折叠速率对变性剂浓度的线性依赖性以及荧光信号不存在未解释的“爆发相”变化，表明两态折叠模型足以描述折叠途径。在存在稳定添加剂0.23 M硫酸钠和1 M氯化钠的情况下进行折叠时，也观察到了这种行为。这些结果强调，当折叠是异质的或折叠速率常数接近检测极限时，在解释偏离理想两态“V形”行为时需要谨慎。
