Substrate protein dependence of GroEL–GroES interaction cycle revealed by high-speed atomic force microscopy imaging

A double-ring-shaped tetradecameric GroELcomplex assists proper protein foldingin cooperation with the cochaperonin GroES. The dynamic GroEL– GroESinteraction reflects the allosteric intra- and inter-ring communications and the chaperoninreaction. 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 chaperonincycle has long been controversial. Here, we directly image the dynamic GroEL– GroESinteraction 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 inter...