Abstract: | Using a data set of 250 non-homologous high-resolution globular proteins, a systematic analysis of the conformations that precede and succeed (positions i and i+3) the various classical β-turn types has been carried out. The collective conformation of a specific β-turn type, including the flanking positions, termed motif, has been studied. In all the four turn types, the majority of examples are preceded and succeeded by extended conformation. Some of the other observations are: (1) In a type I β-turn, Gly at position i+ 3 has a higher favorability to occur with positive ø and does not prefer the major motif βαR-αR-β. (2) The left-handed alpha;-helical conformation (alpha;L) is not preferred at both the flanking positions for type I'and II β-turns, (3) The β–β motif is favourable for all the turn types and the motif β–αL very highly favourable for type I. © Munksgaard 1996. |