Chaperonin complex with a newly folded protein encapsulated in the folding chamber

In Escherichia coli the chaperonins GroEL and GroES form a double-ring complex that binds and folds nascent or unfolded proteins. The T4 bacteriophage has its own version of GroES, gp31, that forms a taller folding chamber to fold the major virus capsid protein, gp23. Clare et al. present the structure of gp23–chaperonin complexes showing gp23 encapsulated in the folding chamber. The folding chamber is distorted in order to enclose a large substrate. This is the first study to present an image of a newly folded protein just before its release from the GroEL folding chamber.