OccK channels from pseudomonas aeruginosa exhibit diverse single-channel electrical signatures but conserved anion selectivity

Jiaming Liu, Elif Eren, Jagamya Vijayaraghavan, Belete R. Cheneke, Mridhu Indic, Bert Van Den Berg, Liviu Movileanu

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Abstract

Pseudomonas aeruginosa is a Gram-negative bacterium that utilizes substrate-specific outer membrane (OM) proteins for the uptake of small, water-soluble nutrients employed in the growth and function of the cell. In this paper, we present for the first time a comprehensive single-channel examination of seven members of the OM carboxylate channel K (OccK) subfamily. Recent biochemical, functional, and structural characterization of the OccK proteins revealed their common features, such as a closely related, monomeric, 18-stranded β-barrel conformation with a kidney-shaped transmembrane pore and the presence of a basic ladder within the channel lumen. Here, we report that the OccK proteins exhibited fairly distinct unitary conductance values, in a much broader range than previously expected, which includes low (∼40-100 pS) and medium (∼100-380 pS) conductance. These proteins showed diverse single-channel dynamics of current gating transitions, revealing one-open substate (OccK3), two-open substate (OccK4-OccK6), and three-open substate (OccK1, OccK2, and OccK7) kinetics with functionally distinct conformations. Interestingly, we discovered that anion selectivity is a conserved trait among the members of the OccK subfamily, confirming the presence of a net pool of positively charged residues within their central constriction. Moreover, these results are in accord with an increased specificity and selectivity of these protein channels for negatively charged, carboxylate-containing substrates. Our findings might ignite future functional examinations and full atomistic computational studies for unraveling a mechanistic understanding of the passage of small molecules across the lumen of substrate-specific, β-barrel OM proteins.

Original languageEnglish (US)
Pages (from-to)2319-2330
Number of pages12
JournalBiochemistry
Volume51
Issue number11
DOIs
StatePublished - Mar 20 2012

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Pseudomonas aeruginosa
Anions
Proteins
Substrates
Membrane Proteins
Birth Injuries
Gram-Negative Bacteria
Ion Channels
Constriction
Kidney
Food
Water
Manufactured Materials
Erythrasma
Bufo arenarum
Bronchiolo-Alveolar Adenocarcinoma
Spontaneous Fractures
Molecules
Kinetics

ASJC Scopus subject areas

  • Biochemistry

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Liu, J., Eren, E., Vijayaraghavan, J., Cheneke, B. R., Indic, M., Van Den Berg, B., & Movileanu, L. (2012). OccK channels from pseudomonas aeruginosa exhibit diverse single-channel electrical signatures but conserved anion selectivity. Biochemistry, 51(11), 2319-2330. DOI: 10.1021/bi300066w

OccK channels from pseudomonas aeruginosa exhibit diverse single-channel electrical signatures but conserved anion selectivity. / Liu, Jiaming; Eren, Elif; Vijayaraghavan, Jagamya; Cheneke, Belete R.; Indic, Mridhu; Van Den Berg, Bert; Movileanu, Liviu.

In: Biochemistry, Vol. 51, No. 11, 20.03.2012, p. 2319-2330.

Research output: Contribution to journalArticle

Liu, J, Eren, E, Vijayaraghavan, J, Cheneke, BR, Indic, M, Van Den Berg, B & Movileanu, L 2012, 'OccK channels from pseudomonas aeruginosa exhibit diverse single-channel electrical signatures but conserved anion selectivity' Biochemistry, vol 51, no. 11, pp. 2319-2330. DOI: 10.1021/bi300066w
Liu J, Eren E, Vijayaraghavan J, Cheneke BR, Indic M, Van Den Berg B et al. OccK channels from pseudomonas aeruginosa exhibit diverse single-channel electrical signatures but conserved anion selectivity. Biochemistry. 2012 Mar 20;51(11):2319-2330. Available from, DOI: 10.1021/bi300066w

Liu, Jiaming; Eren, Elif; Vijayaraghavan, Jagamya; Cheneke, Belete R.; Indic, Mridhu; Van Den Berg, Bert; Movileanu, Liviu / OccK channels from pseudomonas aeruginosa exhibit diverse single-channel electrical signatures but conserved anion selectivity.

In: Biochemistry, Vol. 51, No. 11, 20.03.2012, p. 2319-2330.

Research output: Contribution to journalArticle

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AU - Eren,Elif

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AU - Indic,Mridhu

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N2 - Pseudomonas aeruginosa is a Gram-negative bacterium that utilizes substrate-specific outer membrane (OM) proteins for the uptake of small, water-soluble nutrients employed in the growth and function of the cell. In this paper, we present for the first time a comprehensive single-channel examination of seven members of the OM carboxylate channel K (OccK) subfamily. Recent biochemical, functional, and structural characterization of the OccK proteins revealed their common features, such as a closely related, monomeric, 18-stranded β-barrel conformation with a kidney-shaped transmembrane pore and the presence of a basic ladder within the channel lumen. Here, we report that the OccK proteins exhibited fairly distinct unitary conductance values, in a much broader range than previously expected, which includes low (∼40-100 pS) and medium (∼100-380 pS) conductance. These proteins showed diverse single-channel dynamics of current gating transitions, revealing one-open substate (OccK3), two-open substate (OccK4-OccK6), and three-open substate (OccK1, OccK2, and OccK7) kinetics with functionally distinct conformations. Interestingly, we discovered that anion selectivity is a conserved trait among the members of the OccK subfamily, confirming the presence of a net pool of positively charged residues within their central constriction. Moreover, these results are in accord with an increased specificity and selectivity of these protein channels for negatively charged, carboxylate-containing substrates. Our findings might ignite future functional examinations and full atomistic computational studies for unraveling a mechanistic understanding of the passage of small molecules across the lumen of substrate-specific, β-barrel OM proteins.

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