Influence of medium and long range interactions in different structural classes of globular proteins

An analysis of the dependence known three dimensional structure of globular proteins on their residue contacts and their interactions provides much information about their folding and stability. In this work, we analyse the residue-residue contacts and the role of medium and long range interactions in globular proteins belonging to different structural classes. The results show that while medium range interactions predominate in all alpha class proteins, long range interactions predominate in all beta class. The residues Pro and Gly are found to have lowest medium range contacts, probably due to their helix breaking tendency. The hydrophobic residues Ile, Val and Tyr have higher long range contacts, and hence may serve as good nucleation centres. Further, the role of charged residues and disulfide bridges in these interactions are also discussed.