Figure 1.

(A) Amino acid sequences of calmodulin inhibitory peptide RS-20 and variants containing glutamate (E), tyrosine (Y), and caged tyrosine (cgY). Peptide and caged peptide structures were confirmed by amino acid composition and mass spectrometry (see Materials and Methods). (B) Effects of RS-20 peptides on Ca²⁺/calmodulin-dependent MLCK activity in vitro. 5cgY-RS-20 before (•) and after (○) photoconversion; the photoreleased peptide was indistinguishable from authentic 5Y-RS-20 in inhibitory potency, chromatographic behavior, and mass spectra. There was no detectable inhibition by 5E-RS-20 (▵), whereas 5,18cgY-RS-20 inhibited only weakly both before (▴) and after photolysis (▪). Data points represent means of triplicate measurements with SEM values less than 10% of the mean. (C) Structure and photolysis reaction of cgY.