scholarly journals Differential Regulation of Two Oligogalacturonate Outer Membrane Channels, KdgN and KdgM, of Dickeya dadantii (Erwinia chrysanthemi)

2007 ◽  
Vol 189 (16) ◽  
pp. 5955-5962 ◽  
Author(s):  
Guy Condemine ◽  
Alexandre Ghazi
Keyword(s):  
Outer Membrane ◽  
Virulence Genes ◽  
Outer Membrane Proteins ◽  
Differential Regulation ◽  
Erwinia Chrysanthemi ◽  
Membrane Channels ◽  
Rich Medium ◽  
Positive Potential ◽  
Dickeya Dadantii ◽  
Opposite Manner

ABSTRACT The entry of oligogalacturonates into Dickeya dadantii occurs through the specific channel KdgM. The genome of the bacterium encodes a second member of this family of outer membrane proteins, KdgN. We showed that this protein is also involved in the uptake of oligogalacturonates. When KdgN was reconstituted in proteoliposomes, it formed channels with a conductance of about 450 pS at a positive potential. These channels had weak anionic selectivity. The regulation of kdgN is complex, and five genes controlling the expression of kdgN have been identified: kdgR, pecS, ompR, hns, and crp. Moreover, kdgN was regulated by growth phase but only when bacteria were grown in rich medium. Most of these regulators of kdgN also control kdgM expression, but some of them regulate kdgM in the opposite manner: while PecS and OmpR are repressors of kdgM, they are activators of kdgN. This pattern resembles the regulation of the Escherichia coli general porins OmpF and OmpC, but such opposite regulation of two specific outer membrane channels has never been described before. KdgN may allow the bacteria to collect oligogalacturonates under saprophytic conditions, when virulence genes, including kdgM, are not expressed.

Electrophysiological Characterization of Transport Across Outer Membrane Channels from Gram-Negative Bacteria in Their Native Environment

2019 ◽  
Author(s):  
Jiajun Wang ◽  
Rémi Terrasse ◽  
Jayesh Arun Bafna ◽  
Lorraine Benier ◽  
Mathias Winterhalter
Keyword(s):  
Outer Membrane ◽  
Lipid Membrane ◽  
Membrane Vesicles ◽  
Outer Membrane Vesicles ◽  
Multi Drug Resistance ◽  
Gram Negative Bacteria ◽  
Membrane Channels ◽  
Gram Negative ◽  
Electrophysiological Characterization

Multi-drug resistance in Gram-negative bacteria is often associated with low permeability of the outer membrane. To investigate the role of membrane channels in the uptake of antibiotics, we extract, purify and reconstitute them into artificial planar membranes. To avoid this time-consuming procedure, here we show a robust approach using fusion of native outer membrane vesicles (OMV) into planar lipid bilayer which moreover allows also to some extend the characterization of membrane protein channels in their native environment. Two major membrane channels from <i>Escherichia coli</i>, OmpF and OmpC, were overexpressed from the host and the corresponding OMVs were collected. Each OMV fusion revealed surprisingly single or only few channel activities. The asymmetry of the OMV´s translates after fusion into the lipid membrane with the LPS dominantly present at the side of OMV addition. Compared to conventional reconstitution methods, the channels fused from OMVs containing LPS have similar conductance but a much broader distribution. The addition of Enrofloxacin on the LPS side yields somewhat higher association (<i>k<sub>on</sub></i>) and lower dissociation (<i>k<sub>off</sub></i>) rates compared to LPS-free reconstitution. We conclude that using outer membrane vesicles is a fast and easy approach for functional and structural studies of membrane channels in the native membrane.

scholarly journals The Conservation of Low Complexity Regions in Bacterial Proteins Depends on the Pathogenicity of the Strain and Subcellular Location of the Protein

Genes ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 451
Author(s):  
Pablo Mier ◽  
Miguel A. Andrade-Navarro
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Bacterial Species ◽  
Outer Membrane Proteins ◽  
Subcellular Location ◽  
Low Complexity ◽  
Extracellular Proteins ◽  
Bacterial Strains ◽  
Bacterial Proteins ◽  
Protein Subcellular Location

Low complexity regions (LCRs) in proteins are characterized by amino acid frequencies that differ from the average. These regions evolve faster and tend to be less conserved between homologs than globular domains. They are not common in bacteria, as compared to their prevalence in eukaryotes. Studying their conservation could help provide hypotheses about their function. To obtain the appropriate evolutionary focus for this rapidly evolving feature, here we study the conservation of LCRs in bacterial strains and compare their high variability to the closeness of the strains. For this, we selected 20 taxonomically diverse bacterial species and obtained the completely sequenced proteomes of two strains per species. We calculated all orthologous pairs for each of the 20 strain pairs. Per orthologous pair, we computed the conservation of two types of LCRs: compositionally biased regions (CBRs) and homorepeats (polyX). Our results show that, in bacteria, Q-rich CBRs are the most conserved, while A-rich CBRs and polyA are the most variable. LCRs have generally higher conservation when comparing pathogenic strains. However, this result depends on protein subcellular location: LCRs accumulate in extracellular and outer membrane proteins, with conservation increased in the extracellular proteins of pathogens, and decreased for polyX in the outer membrane proteins of pathogens. We conclude that these dependencies support the functional importance of LCRs in host–pathogen interactions.

Millisecond-Long Simulations of Antibiotics Transport through Outer Membrane Channels

2020 ◽  
Author(s):  
Vinaya Kumar Golla ◽  
Jigneshkumar Dahyabhai Prajapati ◽  
Ulrich Kleinekathöfer
Keyword(s):  
Outer Membrane ◽  
Membrane Channels
Sign in / Sign up

Export Citation Format

Share Document