HUNDREDS OF ANKYRIN-LIKE REPEATS IN FUNCTIONALLY DIVERSE PROTEINS - MOBILE MODULES THAT CROSS PHYLA HORIZONTALLY

Based on pattern searches and systematic database screening, almost 65 0 different ankyrin-like (ANK) repeats from nearly all phyla have been identified; more than 150 of them are reported here for the first tim e. Their presence in functionally diverse proteins such as enzymes, to xins, and transcription factors strongly suggests domain shuffling, bu t their occurrence in prokaryotes and yeast excludes exon shuffling. T he spreading mechanism remains unknown, but in at least three cases ho rizontal gene transfer appears to be involved. ANK repeats occur in at least four consecutive copies. The terminal repeats are more variable in sequence. One feature of the internal repeats is a predicted centr al hydrophobic alpha-helix, which is likely to interact with other rep eats. The functions of the ankyrin-like repeats are compatible with a role in protein-protein interactions. (C) 1993 Wiley-Liss, Inc.