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.