TURN-BASED HYDROPHOBIC POCKET ARE ABLE TO FORM DIASTEREOMERIC PAIRS OF COMPLEXES

Turn sequences are common motif of recognition sites in proteins. Receptors recognition, substrate specificity, and catalytic function generally reside in these loop region that often connect residues of the ?-helices and ?-strand contributing to the stability of proteins tertiary structure. The ?-turn is the simplest defined loop structure with conformational characteristics determined by residues at two positions (i+1, i+2). The early systematic classification of ?-turn reveals a wide variety of geometries and size of loop. A reverse turn is a region of the polypeptide having a hydrogen bond from one main chain carbonyl oxygen (i) to the main chain N-H group three residues along the chain (i+3). Revers turns are very abundant in globular proteins and generally occur at the surface of the molecule. Revers turn are ideal sites for receptor recognition because they present side chain in a solvent accessible arrangement around compact folding of the peptide backbone. It has been suggested that turn regions act as nucleation centres during protein folding.