Abstract

The E.coli, chaperonin machine (GroEL-GroES) is responsible for folding 15% of the newly-synthesized proteins in particular those with complex 3D structures. Bacteriophages like lambda and T5 utilise the host’s chaperonin machinery for the folding of some of their protein structures. Interestingly bacteriophage T4 requires a hybrid GroEL-gp31 chaperonin complex for the folding of the major capsid protein. Although the amino acid sequence of gp31 and GroES is only 14% identical the overall structure appears similar. Cryo electron microscopy and image reconstruction of the GroEL-gp31-ADP complex revealed that the folding cavity is slightly larger than of the GroEL-GroES-ADP complex, which is consistent with the size of the capsid protein (56kDa) that is close to the maximum size that is thought to fit inside the folding cage. It is not fully understood why GroES is unable to assist the folding of the T4 capsid protein. Stuctural and dynamics analysis of the chaperonin-assisted folding of the capsid protein will be presented and the molecular requirements for folding will be discussed.