The kelch repeat superfamily of proteins: propellers of cell function

The kelch motif was discovered as a sixfold tandem element in the sequence of the Drosophila kelch ORF1 protein. The repeated kelch motifs predict a c onserved tertiary structure, a P-propeller. This module appears in many dif ferent polypeptide contexts and contains multiple potential protein-protein contact sites. Members of this growing superfamily are present throughout the cell and extracellularly ann have diverse activities. In this review, w e discuss current information concerning the structural organization of kel ch repeat proteins, their biological roles and the molecular basis of their action.