The N terminus of the molecular chaperonin GroEL is a crucial structural element for its assembly.

The Escherichia coli heat-shock protein GroEL is a member of the highly conserved family of tetradecameric chaperonins 60, which assist in the folding and assembly of other proteins. Using site-directed mutagenesis, it is shown that replacement of the absolutely conserved amino acid residue Lys-3 by arginine or isoleucine destabilizes the GroEL particle and that the replacement Lys-3-->Glu completely blocks its formation. The rank order of effects of these mutations on the stability of the GroEL particle correlates with the associated changes in net charge at that position. Our results show that the N terminus of GroEL is a crucial structural element for its assembly.