CALMODULIN-BINDING PEPTIDE COMPRISING ALPHA-CASEIN EXORPHIN SEQUENCE

Although not homologous to any known calmodulin binding sequences, alp ha(s1)-casein 90-109 (RYLGYLEQLLRLKKYKVPQL), the initial seven residue s corresponding to alpha-casein exorphin sequence, seems to be endowed with the molecular feature characteristic of this class of peptides: a higher proportion of basic and hydrophobic residues. alpha(s1)-Casei n 90-109 was synthesized, and its calmodulin binding was examined. alp ha(s1)-Casein 90-109 reduced the calmodulin-induced cyclic nucleotide phosphodiesterase activation at the comparable concentration to that p reviously reported for endogenous opioid peptides such as beta-endorph in and dynorphin. alpha(s1)-Casein 90-109 as well as the endogenous op ioid peptides shares the common structural motif matching for the inte racting domains of calmodulin in the previously proposed complex model , suggesting that these opioid peptides may interact with calmodulin i n a similar manner.