THE GREEK KEY MOTIF - EXTRACTION, CLASSIFICATION AND ANALYSIS

The Greek key is a very common structural motif in proteins. It has be en traditionally defined as four beta-strands with '+3,-1,-1' topology . This definition encompasses motifs with several different three-dime nsional structures. We have classified Greek keys, based on their hydr ogen bonding patterns, into three groups with similar three-dimensiona l structures. All examples of Greek keys in each of these classes have been automatically extracted using a set of programs. Analysis of the se examples shows the variability of secondary structure segment lengt h and sequences of Greek keys even within one class. This variability suggests that no single folding pathway is likely to fit all Greek key structures.