DISCOVERING PROTEIN SECONDARY STRUCTURES - CLASSIFICATION AND DESCRIPTION OF ISOLATED ALPHA-TURNS

Irregular protein secondary structures are believed to be important st ructural domains involved in molecular recognition processes between p roteins, in interactions between peptide substrates and receptors, and in protein folding. In these respects tight turns are being studied i n detail. They also represent template structures for the design of ne w molecules such as drugs, pesticides, or antigens. Isolated alpha-tur ns, not participating in alpha-helical structures, have received littl e attention due to the overwhelming presence of other types of tight t urns in peptide and protein structures. The growing number of protein X-ray structures allowed us to undertake a systematic search into the Protein Data Bank of this uncharacterized protein secondary structure. A classification of isolated alpha-turns into different types, based on conformational similarity, is reported here. A preliminary analysis on the occurrence of some particular amino acids in certain positions of the turned structure is also presented. (C) 1996 John Wiley & Sons , Inc.