Abstract
A double-ring-shaped tetradecameric GroEL complex assists proper protein folding in cooperation with the cochaperonin GroES. The dynamic GroEL-GroES interaction reflects the allosteric intra- and inter-ring communications and the chaperonin reaction. Therefore, revealing this dynamic interaction is essential to understanding the allosteric communications and the operation mechanism of GroEL. Nevertheless, how this interaction proceeds in the chaperonin cycle has long been controversial. Here, we directly image the dynamic GroEL-GroES interaction under conditions with and without foldable substrate protein using high-speed atomic force microscopy. Then, the imaging results obtained under these conditions and our previous results in the presence of unfoldable substrate are compared. The molecular movies reveal that the entire reaction pathway is highly complicated but basically identical irrespective of the substrate condition. A prominent (but moderate) difference is in the population distribution of intermediate species: symmetric GroEL : GroES2 and asymmetric GroEL : GroES1 complexes, and GroES-unbound GroEL. This difference is mainly attributed to the longer lifetime of GroEL : GroES1 complexes in the presence of foldable substrate. Moreover, the inter-ring communication, which is the basis for the alternating action of the two rings, occurs at two distinct (GroES association and dissociation) steps in the main reaction pathway, irrespective of the substrate condition.This article is part of a discussion meeting issue 'Allostery and molecular machines'.
Highlights
In bacteria, GroEL assists proper folding of many proteins in cooperation with its cochaperonin GroES [1,2]
In spite of these observations, this model postulates that football complexes appear only as a transient intermediate in the reaction cycle, at the time when GroES binds to the transring just before the completion of GroES release from the cis-ring
We could confirm that football complexes are not briefly subsisting but long-lived intermediates with lifetime of 1.522.0 s (Type I) or 1.922.6 s (Type II)
Summary
GroEL assists proper folding of many proteins in cooperation with its cochaperonin GroES [1,2]. The structural basis of this abolishment of inter-ring negative cooperativity has recently been revealed by the atomic structure of football complexes formed by a GroEL mutant with a very low ATPase activity [23] In spite of these observations (for more details, see [24]), this model postulates that football complexes appear only as a transient intermediate in the reaction cycle, at the time when GroES binds to the transring just before the completion of GroES release from the cis-ring. In the present HS-AFM study, we image the GroEL–GroES interaction in the absence and presence of foldable SP and compare the reaction schemes obtained under the three substrate conditions
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