Antiamoebin can function as a carrier or as a pore-forming peptaibol

Antiamoebin is a 16-residue polypeptide whose crystal structure and lytic a ctivity in membrane vesicles have recently been reported. It is a bent heli cal molecule and a member of the peptaibol family of antibiotics. Under con ditions which produce voltage-dependent conductance activity by other membe rs of the family, no single-channel conductance was detected for antiamoebi n, and a carrier-like mechanism was put forward to account for its mode of action. We now present evidence for pore formation that is largely voltage- insensitive, with large amplitude single-channel events on top of a backgro und conductance that may account for the previously proposed carrier-like a ctivity. Thus, antiamoebin may be the first instance of a peptide which can function both as an ion carrier and a pore former. (C) 1998 Elsevier Scien ce B.V. All rights reserved.