KINETIC PARAMETERS OF SINGLE ION CHANNELS AND STATIONARY CONDUCTIVITIES OF PHYTOTOXIN
MODIFIED LIPID BILAYERS
O. S. Ostroumova,1 Ph. A. Gurnev,1 J. Y. Takemoto,2
L. V. Schagina,1 * V. V. Malev 1, 3
1 Institute of Cytology, RAS, St. Petersburg, 2 Utah State University, Logan,
Utah, USA, and 3 St. Petersburg State University, Russia;
* e-mail: lvschag@mail.cytspb.rssi.ru
As shown earlier, phytotoxins produced by Pseudomonas syringae pv. syringae form ion channels of
"small" and "large" conductance when incorporated into planar lipid membranes. The multilevel conductance is due to cluster
organization of the channels (Kaulin et al., 1998; Gurnev et al., 2002). In this study the kinetic parameters of syringomycin E (SRE)
and syringostatin A (SSA) channels in negatively charged bilayer lipid membranes were estimated. The average time of open state of
the small channels (tSopen) did not depend on transmembrane voltage (in the range
of ± 200 mV). The channel characteristics differed between two phytotoxins: the tSopen
for the SRE-channels was much larger than that for SSA-channels. An energetic diagram with two non-conducting states illustrating
the formation of the small channel is proposed to explain the voltage independence of the kinetic parameters. The probability for
synchronous functioning of small channels with SSA was higher than that with SRE. To analyse the role of the clusters in the
biological activities of SRE and SSA, we estimated the cluster contribution to a net transmembrane currents to be 60 and 90 %,
respectively.
Key words: bilayer lipid membranes, cluster organization of ion channels, syringomycin E, syringostatin A
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