Lin Zong, Rye Hays S
Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
Mol Cell. 2004 Oct 8;16(1):23-34. doi: 10.1016/j.molcel.2004.09.003.
The GroEL-GroES chaperonin system is required for the assisted folding of many essential proteins. The precise nature of this assistance remains unclear, however. Here we show that denatured RuBisCO from Rhodospirillum rubrum populates a stable, nonaggregating, and kinetically trapped monomeric state at low temperature. Productive folding of this nonnative intermediate is fully dependent on GroEL, GroES, and ATP. Reactivation of the trapped RuBisCO monomer proceeds through a series of GroEL-induced structural rearrangements, as judged by resonance energy transfer measurements between the amino- and carboxy-terminal domains of RuBisCO. A general mechanism used by GroEL to push large, recalcitrant proteins like RuBisCO toward their native states thus appears to involve two steps: partial unfolding or rearrangement of a nonnative protein upon capture by a GroEL ring, followed by spatial constriction within the GroEL-GroES cavity that favors or enforces compact, folding-competent intermediate states.
GroEL - GroES伴侣蛋白系统是许多必需蛋白质辅助折叠所必需的。然而，这种辅助的确切性质仍不清楚。在这里，我们表明，来自红螺菌的变性核酮糖-1,5-二磷酸羧化酶/加氧酶（RuBisCO）在低温下会形成一种稳定、不聚集且动力学上被困住的单体状态。这种非天然中间体的有效折叠完全依赖于GroEL、GroES和ATP。通过RuBisCO氨基末端和羧基末端结构域之间的共振能量转移测量判断，被困住的RuBisCO单体的重新激活通过一系列GroEL诱导的结构重排进行。因此，GroEL用于将像RuBisCO这样大的、难折叠的蛋白质推向其天然状态的一般机制似乎涉及两个步骤：被GroEL环捕获时非天然蛋白质的部分展开或重排，随后是GroEL - GroES腔内的空间收缩，这有利于或强制形成紧凑的、具有折叠能力的中间状态。
