CH•••O hydrogen bonds at protein-protein interfaces

For the first time, a statistical potential has been developed to quantitatively describe the CH...O hydrogen bonding interaction at the protein-protein interface. The calculated energies of the CH...O pair interaction show a favorable valley at similar to3.3 Angstrom, exhibiting a feature typical of an H-bond and similar to the ab initio quantum calculation result (Scheiner, S., Kar, T., and Gu, Y. (2001) J. Biol. Chem. 276, 9832-9837). The potentials have been applied to a set of 469 protein-protein complexes to calculate the contribution of different types of interactions to each protein complex: the average energy contribution of a conventional H-bond is similar to30%; that of a CH...O H-bond is 17%; and that of a hydrophobic interaction is 50%. In some protein-protein complexes, the contribution of the CH...OH-bond can reach as high as similar to40-50%, indicating the importance of the CH...OH-bond at the protein interface. At the interfaces of these complexes, (CH)-H-alpha...OH-bonds frequently occur between adjacent strands in both parallel and antiparallel orientations, having the obvious structural motif of bifurcated H-bonds. Our study suggests that the weak CH...OH-bond makes an important contribution to the association and stability of protein complexes and needs more attention in protein-protein interaction studies.