Prediction and classification of α‐turn types

Tight turns play an important role in globular proteins from both the structural and functional points of view. Of tight turns, β-turns and γ-turns have been extensively studied, but α-turns were little investigated. Recently, a systematic search for α-turns was conducted by V. Pavone et al. [(1996) Biopolymers, Vol. 38, pp. 705–721] from 190 proteins (221 protein chains). They found 356 α-turns that were classified into nine different types according to their backbone trajectory features. In view of this new discovery, a sequence-coupled model based on Markov chain theory is proposed for predicting the α-turn types in proteins. The high rates of correct prediction by resubstitution test and jackknife test imply that that the formation of different α-turn types is evidently correlated with the sequence of a pentapeptide, and hence can be approximately predicted based on the sequence information of the pentapeptide alone, although the role of its interaction with the other part of a protein cannot be completely ignored. The algorithm presented here can also be used to conduct the prediction in which a distinction between α-turns and non-α-turns is also required. © 1997 John Wiley & Sons, Inc. Biopoly 42: 837–853, 1997