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Blockage of anthrax PA63 pore by a multicharged high-affinity toxin inhibitor.

Authors :
Nestorovich EM
Karginov VA
Berezhkovskii AM
Bezrukov SM
Source :
Biophysical journal [Biophys J] 2010 Jul 07; Vol. 99 (1), pp. 134-43.
Publication Year :
2010

Abstract

Single channels of Bacillus anthracis protective antigen, PA(63), were reconstituted into planar lipid membranes and their inhibition by cationic aminopropylthio-beta-cyclodextrin, AmPrbetaCD, was studied. The design of the highly efficient inhibitor, the sevenfold symmetrical cyclodextrin molecule chemically modified to add seven positive charges, was guided by the symmetry and predominantly negative charge of the PA(63) pore. The protective action of this compound has been demonstrated earlier at both single-molecule and whole-organism levels. In this study, using noise analysis, statistics of time-resolved single-channel closure events, and multichannel measurements, we find that AmPrbetaCD action is bimodal. The inhibitor, when added to the cis side of the membrane, blocks the channel reversibly. At high salt concentrations, the AmPrbetaCD blockage of the channel is well described as a two-state Markov process, in which both the on- and off-rates are functions of the salt concentration, whereas the applied voltage affects only the off-rate. At salt concentrations smaller than 1.5 M, the second mode of AmPrbetaCD action on the channel is discovered: addition of the inhibitor enhances voltage gating, making the closed states of the channel more favorable. The effect depends on the lipid composition of the membrane.<br /> (Copyright 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.)

Details

Language :
English
ISSN :
1542-0086
Volume :
99
Issue :
1
Database :
MEDLINE
Journal :
Biophysical journal
Publication Type :
Academic Journal
Accession number :
20655841
Full Text :
https://doi.org/10.1016/j.bpj.2010.03.070