title: Melittin and a chemically modified trichotoxin form alamethicin-type multi-state pores.
abstract: The bee venom constituent, melittin, is structurally and functionally related to alamethicin. By forming solvent-free planar bilayers of small area (approx. 100 microns 2) on the tip of fire-polished glass pipettes we could observe single melittin pores in these membranes. An increase in the applied voltage induced further non-integral conductance levels. This indicates that melittin forms multi-level pores similar to those formed by alamethicin. Trichotoxin A40, an antibiotic analogue of alamethicin, also induces a voltage-dependent bilayer conductivity, but no stable pore states are resolved. However, chemical modification of the C-terminal molecule part by introduction of a dansyl group leads to a steeper voltage-dependence and pore state stabilization. Comparing structure and activity of several natural and synthetic amphiphilic polypeptides, we conclude that a lipophilic, N-terminal alpha-helical part of adequate length (dipole moment) and a large enough hydrophilic, C-terminal region are sufficient prerequisites for voltage-dependent formation of multi-state pores.
mesh_terms: D000408:Alamethicin; D000900:Anti-Bacterial Agents; D001514:Bee Venoms; D008051:Lipid Bilayers; D008555:Melitten; D008968:Molecular Conformation; D010455:Peptides; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D011487:Protein Conformation
chemical_list: D000900:Anti-Bacterial Agents; D001514:Bee Venoms; D008051:Lipid Bilayers; D010455:Peptides; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D008555:Melitten; D000408:Alamethicin; C077907:trichotoxin A40; C028694:1-palmitoyl-2-oleoylphosphatidylcholine