Chaperonin-assisted protein folding. The E. coli chaperonins GroEL and GroES. Each GroEL complex consists of two chambers formed by two heptameric rings (each subunit M_r 57,000). GroES, also a heptamer (each subunit M_r 10,000), blocks one of the GroEL pockets. Surface (left) and cut-away (right) images of the GroEL/GroES complex are shown.