title: Lytic activity and structural differences of amphipathic peptides derived from trialysin.
abstract: Trialysin is a pore-forming protein found in the saliva of Triatoma infestans (Hemiptera, Reduviidae), the insect vector of Chagas' disease. The protein is active against a broad range of cell types from bacteria to eukaryotic cells. Recognizing that the N-terminus of trialysin harbors the lytic motif [Amino, R., Martins, R. M., Procopio, J., Hirata, I. Y., Juliano, M. A., and Schenkman, S. (2002) J. Biol. Chem. 277, 6207-6213], we designed a set of peptides scanning this region to investigate the structural basis of its biological function. Peptides encompassing residues 1-32 (P6), 1-27 (P7), and 6-32 (P5) efficiently induced lysis of the protozoan parasite Trypanosoma cruzi and Escherichia coli in the 0.4-9.0 microM range, while much higher concentrations were required to cause hemolysis. Other more internal peptides, including peptide P2 (residues 21-47) and others up to residue 52, were less effective. P6 turned out to be the most active of all. P7 has a significantly higher activity than P5 against E. coli, while P5 has a hemolytic activity comparable to that of P6. CD spectroscopy showed that all tested peptides acquire a comparable helical content in solvent mixtures or in detergent micelles. The solution structure of P2 and P5-P7 was determined in a 30% trifluoroethanol/water mixture by nuclear magnetic resonance. All peptides exhibit a structure characterized by a central helical fold, and except for P2, which does not show a continuous hydrophobic surface, they are amphipathic. The structural models show that P5 and P7 extend their structural similarities with the most active peptide, P6, in either the C-terminus or the N-terminus. Amino acid substitutions in the N-terminus of P6 improved hemolysis but did not change the activity against T. cruzi. These results suggest that while amphipathicity is essential for the lytic activity, the selectivity of the active peptides for specific organisms appears to be associated with the structural features of their N- and C-termini.
authors.affiliation: Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo, R. Botucatu 862, São Paulo 04023-062, Brazil.
authors.forename: Rafael M
authors.initials: RM
authors.lastname: Martins
authors.forename: Maurício L
authors.initials: ML
authors.lastname: Sforça
authors.forename: Rogério
authors.initials: R
authors.lastname: Amino
authors.forename: Maria Aparecida
authors.initials: MA
authors.lastname: Juliano
authors.forename: Sérgio
authors.initials: S
authors.lastname: Oyama
authors.forename: Luiz
authors.initials: L
authors.lastname: Juliano
authors.forename: Thelma A
authors.initials: TA
authors.lastname: Pertinhez
authors.forename: Alberto
authors.initials: A
authors.lastname: Spisni
authors.forename: Sergio
authors.initials: S
authors.lastname: Schenkman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002463:Cell Membrane Permeability / Q000187:drug effects*; D014355:Chagas Disease / Q000188:drug therapy; D002942:Circular Dichroism; D004926:Escherichia coli / Q000187:drug effects*; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D010455:Peptides / Q000737:chemistry / Q000494:pharmacology; D011487:Protein Conformation; D012471:Salivary Proteins and Peptides / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D012997:Solvents / Q000737:chemistry; D014224:Triatoma / Q000737:chemistry*; D014349:Trypanosoma cruzi / Q000187:drug effects*
chemical_list: D008823:Micelles; D010455:Peptides; D012471:Salivary Proteins and Peptides; D012997:Solvents; C509988:trialysin protein, Triatoma infestans