Reversals of polypeptide chain in globular proteins.

A simple algorithm has been developed to detect beta-bends and 'loops'-chain reversals containing five amino acid residues, using only coordinates of C alpha-atoms from crystal structure data of globular proteins using the above algorithm. Analysis of bends have showed that the total number of bends in each protein (TB) is linearly related to total number of non-hydrophobic residues in that protein which in turn is related linearly to total number of amino acid residues. Secondly, we found that a large number of consecutive bends occur in each protein which give rise to on an average only three independent residues per turn. Positional preference of amino acid residues in chain reversals is stressed. Consideration of pairs of amino acid residues in positions (i + 1) and (i + 2) of bends seems to provide a more reliable basis for predicting chain reversals in proteins.