Ca2+/Calmodulin-binding proteins from the C. elegans proteome

Calmodulin (CaM) is the primary Ca2+-sensor that regulates a wide variety of cellular processes in eukaryotes. Although many Ca2+/CaM-binding proteins have been identified, very few such proteins could be found from the genome-wide protein–protein interaction maps of Caenorhabditis elegans constructed by yeast two-hybrid screening. Using a genotype–phenotype conjugation method called mRNA-display, we performed a selection for Ca2+/CaM-binding proteins from a proteome library of C. elegans. The method allowed the identification of 9 known and 47 previously uncharacterized Ca2+-dependent CaM-binding proteins from the adult worm proteome. The Ca2+/CaM-binding properties of these proteins were characterized and their binding motifs were identified. The availability of such information could facilitate our understanding of the signaling pathways mediated by Ca2+/CaM in C. elegans. Due to its simplicity and efficiency, the method could be readily applied to examine the Ca2+-dependent binding partners of numerous other Ca2+-binding proteins, which may play important roles in many signaling pathways in C. elegans.