CONDUCTANCE OF PHYTOTOXIN CHANNELS IN THE PRESENCE OF LARGE ORGANIC IONS
O. S. Ostroumova,1 S. S. Efimova, L. V. Schagina
Institute of Cytology RAS, St. Petersburg;
1 e-mail: ostroumova@mail.cytspb.rssi.ru
In this study we evaluated the effect of penetrating anion size on the properties of the channels formed by
cyclic lipodepsipeptide syringomycin E (SRE) in bilayer lipid membranes. Conductance and the mean lifetime
of the SRE channels have been measured in 0.4 M solutions of sodium chloride, aspartate, and gluconate. Comparison
of the results of conductometrical and electrophysiological measurements has shown: 1) ratio of mobilities
of aspartate anions in the channel and in the water solution is 5 times lower than that for chlorine anions;
2) conductivity of the channels in the presence of sodium gluconate is due mainly to cations. The results obtained
indicate binding of the penetrating anions to the selective filter of the SRE pore. The radius of the SRE
channel selective filter has been established (r ~ 0.3 nm) and its localization in the cis-mouth of the pore has been
found.
Key words: bilayer lipid membranes, channel-forming toxins, single ion channels, selective filter of the pore
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