pH-dependent pore-forming activity of OmpATb from Mycobacterium tuberculosis and characterization of the channel by peptidic dissection

Molle, Virginie, Saint, Nathalie, Campagna, Sylvie, Kremer, Laurent, Lea, Edward, Draper, Philip and Molle, Gérard (2006) pH-dependent pore-forming activity of OmpATb from Mycobacterium tuberculosis and characterization of the channel by peptidic dissection. Molecular Microbiology, 61 (3). pp. 826-837. ISSN 1365-2958

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Abstract

Mycobacteria are characterized by an unusual cell wall that controls nutrient and small hydrophilic compound permeability. Porin‐like proteins are necessary to ensure the transport of molecules into the cell. Here, we investigated the pore‐forming properties of OmpATb, a porin from Mycobacterium tuberculosis, in lipid bilayers. Multi‐channel experiments showed an asymmetric behaviour with channel closures at negative critical voltages (Vc) and a strong decrease in Vc at acidic pH. Single‐channel experiments gave conductance values of about 850 ± 80 pS in 1 M KCl and displayed a weak cationic selectivity in 4–8 pH range. The production and characterization of a series of truncated OmpATb proteins, showed that the central domain (OmpATb73−220) was sufficient to induce the ion channel properties of the native protein in lipid bilayers, i.e. asymmetric insertion, pH‐dependent voltage closure, cationic selectivity and similar conductance values in 1 M KCl. Western blot analysis suggests that the presence of OmpATb is only restricted to certain pathogenic species. Therefore, the propensity of channels of native OmpATb to close at low pH may represent an intrinsic property allowing pathogenic mycobacteria to adapt and survive to mildly acidic conditions, such as those encountered within the macrophage phagosome.

Item Type: Article
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: LivePure Connector
Date Deposited: 30 Jan 2019 15:30
Last Modified: 21 Apr 2020 19:49
URI: https://ueaeprints.uea.ac.uk/id/eprint/69743
DOI: 10.1111/j.1365-2958.2006.05277.x

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