Cation selectivity is a conserved feature in the OccD subfamily of Pseudomonas aeruginosa

Jiaming Liu, Aaron J. Wolfe, Elif Eren, Jagamya Vijayaraghavan, Mridhu Indic, Bert Van Den Berg, Liviu Movileanu

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


To achieve the uptake of small, water-soluble nutrients, Pseudomonas aeruginosa, a pathogenic Gram-negative bacterium, employs substrate-specific channels located within its outer membrane. In this paper, we present a detailed description of the single-channel characteristics of six members of the outer membrane carboxylate channel D (OccD) subfamily. Recent structural studies showed that the OccD proteins share common features, such as a closely related, monomeric, 18-stranded β-barrel conformation and large extracellular loops, which are folded back into the channel lumen. Here, we report that the OccD proteins displayed single-channel activity with a unitary conductance covering an unusually broad range, between 20 and 670 pS, as well as a diverse gating dynamics. Interestingly, we found that cation selectivity is a conserved trait among all members of the OccD subfamily, bringing a new distinction between the members of the OccD subfamily and the anion-selective OccK channels. Conserved cation selectivity of the OccD channels is in accord with an increased specificity and selectivity of these proteins for positively charged, carboxylate-containing substrates.

Original languageEnglish (US)
Pages (from-to)2908-2916
Number of pages9
JournalBiochimica et Biophysica Acta - Biomembranes
Issue number11
StatePublished - Nov 2012


  • Single-channel electrical recording
  • Single-molecule biophysics
  • Spontaneous gating
  • The OccD subfamily
  • The OprD family

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology


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