Paradoxical one-ion pore behavior of the long β-helical peptide of marine cytotoxic polytheonamide B.

ABSTRACT: The cytotoxic 48-mer peptide, polytheonamide B (pTB), from a marine sponge forms a β(6.3)-helix with an inner diameter of 4 Å and a length of 45 Å, features that allow the selective permeation of monovalent cations across targeted cell membranes. To characterize this long, narrow pore, electrophysiological examination using a planar lipid bilayer method was performed. The single-channel current amplitude exhibited saturation for concentrated Cs(+) or K(+) solution, and the reversal potential in mixed solutions did not exhibit any anomalous mole-fraction behavior. These results suggest the one-ion permeation mechanism. This is in contrast to the short (26 Å) β(6.3)-helical gramicidin channel, which holds two ions simultaneously. The paradoxical one-ion permeation through the long pTB channe

SUBMITTER: Iwamoto M 

PROVIDER: S-EPMC3887386 | biostudies-literature | 2014 Jan

REPOSITORIES: biostudies-literature