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Evidence for a small anion‐selective channel in the cell wall ofMycobacterium bovis BCG besides a wide cation‐selective pore
Author(s) -
Thomas Lichtinger,
Béate Heym,
Elke Maier,
Helga Eichner,
Stewart T. Cole,
Roland Benz
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)00844-3
Subject(s) - citation , mycobacterium bovis , channel (broadcasting) , computer science , ion , chemistry , information retrieval , world wide web , medicine , mycobacterium tuberculosis , computer network , pathology , organic chemistry , tuberculosis
Two channels were observed in extracts of whole Mycobacterium bovis BCG cells using organic solvents and detergents. The channels derived from organic solvent treatment had a single-channel conductance of about 4.0 nS in 1 M KCl in lipid bilayer membranes with properties similar to those of the channels discovered previously in Mycobacterium smegmatis and Mycobacterium chelonae. The channel was in its open configuration only at low transmembrane potentials. At higher voltages it switched to closed states that were almost impermeable for ions. Lipid bilayer experiments in the presence of detergent extracts of whole cells revealed another channel with a single-channel conductance of only 780 pS in 1 M KCl. Our results indicate that the mycolic acid layer of M. bovis BCG contains two channels, one is cation-selective and its permeability properties can be finely controlled by cell wall asymmetry or potentials. The other one is anion-selective, has a rather small single-channel conductance and is voltage-insensitive. The concentration of channel-forming proteins in the cell wall seems to be small, which is in agreement with the low cell wall permeability for hydrophilic solutes.