Three novel peptides were isolated from the venomous saliva of predatory reduviids. They were identified by mass spectrometry and HPLC analysis and consist of 34-36 amino acid residues. They are relatively homologous to the calcium channel blockers omega-conotoxins from marine cone snails and belong to the four-loop Cys scaffold structural class. Ptu1, the shortest peptide, was chemically synthesized (sPtu1) and co-eluted with its native form. Circular dichroism spectra of the sPtu1 showed a high content of beta-turns similar to that of omega-conotoxins GVIA and MVIIA. Electrophysiological experiments demonstrated that sPtu1 reversibly blocks the N-type calcium channels expressed in BHK cells.