Binding of ¹²⁵I-labeled 14-3-3ζ to synthetic peptides corresponding to the 14-3-3 binding region of β_c. Microtiter wells were coated with synthetic peptides CLGPPHSRSLPDILG either nonphosphorylated or phosphorylated on the second serine (underlined). Various concentrations of¹²⁵I-labeled recombinant 14-3-3ζ protein were added to microtiter wells and incubated at 22°C for 2 hours. (Insert) Scatchard analyses of 14-3-3 interaction with the serine-phosphorylated peptide.