Gramicidin tryptophans mediate formamidinium-induced channel stabilization

Biophysical Journal
S A Seoh, D D Busath

Abstract

Compared with alkali metal cations, formamidinium ions stabilize the gramicidin A channel molecule in monoolein bilayers (Seoh and Busath, 1993a). A similar effect is observed with N-acetyl gramicidin channel molecules in spite of the modified forces at the dimeric junction (Seoh and Busath, 1993b). Here we use electrophysiological measurements with tryptophan-to-phenylalanine-substituted gramicidin analogs to show that the formamidinium-induced channel molecule stabilization is eliminated when the four gramicidin tryptophans are replaced with phenylalanines in gramicidin M-. This suggests that the stabilization is mediated by the tryptophan side chains. Tryptophan residues 9, 13, and 15 must cooperate to produce the effect because replacement of any one of the three with phenylalanine significantly reduces stabilization; replacement of Trp-11 with phenylalanine causes negligible decrease in stabilization. In addition, formamidinium-related current-voltage supralinearity and open-channel noise are absent with gramicidin M-. When the lipid bilayer was formed with monoolein ether rather than monoolein ester, the channel lifetimes were reduced markedly and, at low voltage and relative to those in KCl solution, were decreased by a ...Continue Reading

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Citations

Jul 9, 1999·Biopolymers·B M BurkhartV Pletnev
Jan 20, 2010·Interdisciplinary Sciences, Computational Life Sciences·Morad Mustafa, David D Busath
Oct 28, 1998·Biophysical Journal·B M BurkhartW L Duax
Jul 2, 1999·Biophysical Journal·V L ShapovalovY N Antonenko
Jan 14, 2021·Chemical Communications : Chem Comm·Qi XiaoJun-Li Hou
Jun 28, 2019·Chemical Reviews·Emelie FloodToby W Allen

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