(485c) Binding Site Allostery in the E. Coli Groel Chaperonin Subunit

The E. Coli chaperonin GroEL is a member of a class of chaperones thought to be responsible for catalyzing in vivo protein folding. GroEL itself is a double-ring homotetradecamer of ~56kDa subunits, each of which undergoes major conformational rearrangement during a GroEL reaction cycle. Although it requires ATP for its activity, a detailed understanding of the role of ATP in the reaction cycle has been the subject of controversy. Experimental evidence has lead to the suggestion that allosteric communication between an ATP binding site in the equatorial domain of a subunit protein and a peptide binding area in the apical domain is necessary, but the detailed pathway of this communication has so far been unclear. We have performed atomistic molecular dynamics simulations of a solvated subunit protein from the E. Coli GroEL chaperonin to uncover the mechanism of allosteric communication between these nucleotide and peptide binding sites. We have found that bound ATP frustrates the formation of a previously unrecognized interdomain salt triplet connecting the apical domain and the equatorial domain. The additional flexibility of the apical domain afforded by the broken bridge is sufficient to allow it to bury its hydrophobic peptide binding area in an intersubunit junction, supporting the experimental evidence that binding of ATP triggers release of a bound peptide