SUNY at Albany
June 19-23, 2001
From Minichaperone To GroEL: A homage to Paul Sigler
GroEL is a complex, ATP-fuelled, allosteric protein that aids the folding of some proteins. We have been building up its mechanism by first identifying its minimal structural feature required for assisting protein folding and then adding back the stuctural complexity to work out why and how the complex structure is necessary. A domain of some 140 residues was found to have residual refolding activity in the absence of the rest of the protein and of ATP. The crystal structure of the minichaperone provided the first high resolution structural information on GroEL-peptide interactions. On building the structure of the minichaperone into the structure of GroEL determined by Sigler and colleagues, we showed how a peptide substrate can bind to a contiguous ring of binding sites around the neck of GroEL and how the allosteric changes on binding ATP GroEL will weaken the binding and may even distort a misfolded substrate by the ring of sites acting as a rack. An enthusiastic supporter of this initially controversial work was Paul Sigler who used the minichaperone to develop further the model of substrate-binding. We subsequently assembled seven of the minichaperones in a non-allosteric ring to mimic their disposition in intact GroEL to analyse the affect of avidity on folding. We then constructed a single allosteric ring of GroEL to analyse the difference between double and single ring proteins. At each stage of increasing complexity, there is a gain in activity. The minichaperone is a useful practical tool for the refolding of proteins in vitro.
A. R. Fersht, A. M. Buckle, Q. Wang, J. Chatellier, F. Hill
Cambridge Centre for Protein Engineering and Cambridge University Chemical Laboratory, MRC Centre, Hills Road, Cambridge CB2 2QH, UK. E-mail: email@example.com