Subunit Conformational Variation Within Individual GroEL Oligomers Resolved by Cryo-EM.

Significance Using cryo-EM and expanding on focused classification allowed for the bacterial chaperone, GroEL, to be structurally resolved at atomic detail one particle at a time. This approach differs from generating the traditional structural ensemble average of presumably identical particle images. Three dominant subunit conformations were identified, and their spatial distributions were found to be different in each individual GroEL oligomer. This strategy demonstrates the application of cryo-EM to characterize the biophysical properties of structural dynamics of individual molecular machines one at a time.