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

• Published in: Biochimica et biophysica acta 2012-11, Vol.1818 (11), p.2908-2916
• Main Authors: Liu, Jiaming, Wolfe, Aaron J., Eren, Elif, Vijayaraghavan, Jagamya, Indic, Mridhu, van den Berg, Bert, Movileanu, Liviu
• Format: Article
• Language: English
• Subjects: Bacterial Outer Membrane Proteins - chemistry; Bacterial Outer Membrane Proteins - genetics; Cations; Cloning, Molecular; Lipid Bilayers; Pseudomonas aeruginosa - chemistry; Single-channel electrical recording; Single-molecule biophysics; Spontaneous gating; The OccD subfamily; The OprD family
• ISSN: 0005-2736; 0006-3002; 1879-2642
• DOI: 10.1016/j.bbamem.2012.07.009

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 670pS, 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. [Display omitted] ► We present detailed single-channel features of six members of the OccD subfamily. ► OccD proteins displayed a unitary conductance covering a broad range. ► Cation selectivity is a conserved trait among the members of the OccD subfamily.