Detecting the Hydrogen Bond Cooperativity in a Protein β-Sheet by H/D Exchange

The hydrogen bond (H-bond) cooperativity in the beta-sheet of GB3 is investigated by a NMR hydrogen/deuterium (H/D) exchange method. It is shown that the weakening of one backbone N-H...O=C H-bond between two beta-strands, beta 1 and beta 2, due to the exchange of NH to ND of the H-bond donor in beta 1, perturbs the chemical shift of C-13(alpha), C-13(beta), H-1(alpha), H-1(N), and N-15 of the H-bond acceptor and its following residue in beta 2. Quantum mechanical calculations suggest that the -H-bond chemical shift isotope effect is caused by the structural reorganization in response to the H-bond weakening. This structural reorganization perturbs four neighboring H-bonds, with three being weaker and one being stronger, indicating that three H-bonds are cooperative and one is anticooperative with the perturbed H-bond. The sign of the cooperativity depends on the relative position of the H-bonds. This H-bond cooperativity, which contributes to beta-sheet stability overall, can be important for conformational coupling across the beta-sheet.

Automated summary

The hydrogen bond cooperativity in the beta-sheet of GB3 protein is investigated using a NMR hydrogen/deuterium exchange method. It is found that weakening one hydrogen bond perturbs other neighboring hydrogen bonds, with three being cooperative and one being anticooperative. This hydrogen bond cooperativity plays a significant role in the stability and conformational coupling of the beta-sheet.