| Abstract
| - Although not homologous to any known calmodulin binding sequences,αs1-casein 90−109(RYLGYLEQLLRLKKYKVPQL), the initial seven residues corresponding toα-casein exorphinsequence, seems to be endowed with the molecular feature characteristicof this class of peptides: a higher proportion of basic and hydrophobic residues.αs1-Casein 90−109 was synthesized,andits calmodulin binding was examined. αs1-Casein90−109 reduced the calmodulin-induced cyclicnucleotide phosphodiesterase activation at the comparable concentrationto that previously reportedfor endogenous opioid peptides such as β-endorphin and dynorphin.αs1-Casein 90−109 as well asthe endogenous opioid peptides shares the common structural motifmatching for the interactingdomains of calmodulin in the previously proposed complex model,suggesting that these opioidpeptides may interact with calmodulin in a similar manner. Keywords: Calmodulin; casein; exorphin; complex model; opioidpeptide
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