Observation of a unique pattern of bifurcated hydrogen bonds in the crystal structures of the N-glycoprotein linkage region models

Elucidation of the intra- and intermolecular carbohydrate-protein interactions would greatly contribute toward obtaining a better understanding of the structure-function correlations of the protein-linked glycans. The weak interactions involving C-H center dot center dot center dot O have recently been attracting immense attention in the domain of biomolecular recognition. However, there has been no report so far on the occurrence of C-H center dot center dot center dot O hydrogen bonds in the crystal structures of models and analogs of N-glycoproteins. We present herein an analysis of C-H center dot center dot center dot O interactions in the crystal structures of all N-glycoprotein linkage region models and analogs. The study reveals a cooperative network of bifurcated hydrogen bonds consisting of N-H center dot center dot center dot O and C-H center dot center dot center dot O interactions seen uniquely for the models. The cooperative network consists of two antiparallel chains of bifurcated hydrogen bonds, one involving N1-H, C2'-H and O1' of the aglycon moiety and the other involving N2-H, C1-H and O1' of the sugar. Such bifurcated hydrogen bonds between the core glycan and protein are likely to play an important role in the folding and stabilization of proteins.