Howard Hughes Medical Institute, Yale School of Medicine, New Haven, CT 06510, USA.
FEBS Lett. 2011 Jun 23;585(12):1969-72. doi: 10.1016/j.febslet.2011.05.031. Epub 2011 May 20.
Under "permissive" conditions at 25°C, the chaperonin substrate protein DM-MBP refolds 5-10 times more rapidly in the GroEL/GroES folding chamber than in free solution. This has been suggested to indicate that the chaperonin accelerates polypeptide folding by entropic effects of close confinement. Here, using native-purified DM-MBP, we show that the different rates of refolding are due to reversible aggregation of DM-MBP while folding free in solution, slowing its kinetics of renaturation: the protein exhibited concentration-dependent refolding in solution, with aggregation directly observed by dynamic light scattering. When refolded in chloride-free buffer, however, dynamic light scattering was eliminated, refolding became concentration-independent, and the rate of refolding became the same as that in GroEL/GroES. The GroEL/GroES chamber thus appears to function passively toward DM-MBP.
在 25°C 的“宽松”条件下，伴侣蛋白底物蛋白 DM-MBP 在 GroEL/GroES 折叠腔内的重折叠速度比在游离溶液中快 5-10 倍。这表明伴侣蛋白通过紧密约束的熵效应加速多肽折叠。在这里，我们使用天然纯化的 DM-MBP 表明，不同的重折叠速率是由于 DM-MBP 在游离溶液中折叠时可逆聚集，从而减慢了其复性动力学：该蛋白在溶液中表现出浓度依赖性的重折叠，通过动态光散射直接观察到聚集。然而，当在无氯缓冲液中重折叠时，动态光散射消失，重折叠变得与浓度无关，重折叠的速度与在 GroEL/GroES 中的速度相同。因此，GroEL/GroES 腔似乎对 DM-MBP 起被动作用。
