CALP3, a Ca2+-like peptide, is a potent Ca2+ channel blocker that activates EF hand motifs of Ca2+-binding proteins. CALP3 can functionally mimic increased [Ca2+]i by modulating the activity of Calmodulin (CaM), Ca2+ channels and pumps. CALP3 has the potential in controlling apoptosis in diseases such as AIDS or neuronal loss due to ischemia.