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Biophysical Journal 73: 2465-2475 (1997)
© 1997 the Biophysical Society

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Voltage-dependent behavior of a "ball-and-chain" gramicidin channel.

G A Woolley, V Zunic, J Karanicolas, A S Jaikaran and A V Starostin

Department of Chemistry, University of Toronto, Ontario, Canada. awoolley@chem.utoronto.ca

ABSTRACT

The channel-forming properties of two analogs of gramicidin, gramicidin-ethylenediamine (gram-EDA), and gramicidin-N,N-dimethylethylenediamine (gram-DMEDA) were studied in planar lipid bilayers, using protons as the permeant ion. These peptides have positively charged amino groups tethered to their C-terminal ends via a linker containing a carbamate group. Gram-DMEDA has two extra methyl groups attached to the terminal amino group, making it a bulkier derivative. The carbamate groups undergo thermal cis-trans isomerization on the 10-100-ms time scale. The conductance behavior of gram-EDA is found to be markedly voltage dependent, whereas the behavior of gram-DMEDA is not. In addition, voltage affects the cis-trans ratios of the carbamate groups of gram-EDA, but not those of gram-DMEDA. A model is proposed to account for these observations, in which voltage can promote the binding of the terminal amino group of gram-EDA to the pore in a "ball-and-chain" fashion. The bulkiness of the gram-DMEDA derivative prevents this binding.




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Copyright © 1997 by the Biophysical Society.