scholarly journals Bacterial Adaptor Membrane Fusion Proteins and the Structurally Dissimilar Outer Membrane Auxiliary Proteins Have Exchanged Central Domains inα-Proteobacteria

2010 ◽  
Vol 2010 ◽  
pp. 1-5 ◽  
Author(s):  
Anthony Y. Xiao ◽  
Jing Wang ◽  
Milton H. Saier
Keyword(s):  
Membrane Fusion ◽  
Outer Membrane ◽  
Fusion Proteins ◽  
Transport Systems ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Transporter Protein ◽  
Functional Implications ◽  
Membrane Fusion Proteins ◽  
Helical Region

Transport systems frequently include auxiliary proteins that perform subfunctions within the transporter protein complex. Two such proteins found in Gram-negative bacteria are the Membrane Fusion Proteins (MFPs) and the Outer Membrane Auxiliary (OMA) proteins. We here demonstrate that OMAs present inα-proteobacteria (but not in other bacterial types) contain a longα-helical region that is homologous to corresponding regions in the MFPs. The results suggest that during their evolution, OMAs, specifically fromα-proteobacteria, exchanged their ownα-helical domain for one derived from an MFP. The structural and functional implications of these findings are discussed.

Development of New Cloning Vectors for the Production of Immunogenic Outer Membrane Fusion Proteins in Escherichia coli

1996 ◽  
Vol 14 (2) ◽  
pp. 203-208 ◽  
Author(s):  
Pierre Cornells ◽  
Javier Cote Sierra ◽  
Antonio Lim ◽  
Achut Malur ◽  
Sumalee Tungpradabkul ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Membrane Fusion ◽  
Outer Membrane ◽  
Fusion Proteins ◽  
Cloning Vectors ◽  
Membrane Fusion Proteins

scholarly journals Appoptosin interacts with mitochondrial outer-membrane fusion proteins and regulates mitochondrial morphology

2016 ◽  
Vol 129 (5) ◽  
pp. 994-1002 ◽  
Author(s):  
Cuilin Zhang ◽  
Zhun Shi ◽  
Lingzhi Zhang ◽  
Zehua Zhou ◽  
Xiaoyuan Zheng ◽  
...  
Keyword(s):  
Membrane Fusion ◽  
Outer Membrane ◽  
Fusion Proteins ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Morphology ◽  
Membrane Fusion Proteins

scholarly journals Development of transport systems of quinolone class antibiotics through outer membrane vesicles (OMVs) in Gram-negative bacteria

2018 ◽  
Author(s):  
Carlos Fernando Macedo da Silva ◽  
Marcelo Lancellotti
Keyword(s):  
Outer Membrane ◽  
Bacterial Growth ◽  
Membrane Vesicles ◽  
Outer Membrane Vesicles ◽  
Transport Systems ◽  
Gram Negative Bacteria ◽  
Extracellular Medium ◽  
Gram Negative ◽  
Resistance To Antibiotics ◽  
Cell Reproduction

Multi-resistance to antibiotics in Gram-negative bacteria has been reported in several studies, which make more effective methods of controlling and eliminating these bacteria necessary. To overcome multiresistant profiles, we used OMVs (Outer Membrane Vesicles) as carriers of levofloxacin to encapsulate and transport the drug from the extracellular medium into the cell, overcoming resistance barriers and inhibiting cell reproduction machinery. Prepackaged formulations in this manner were quite effective and, in some cases, totally inhibited bacterial growth by making the drug efficient again.

scholarly journals Structure of LetB reveals a tunnel for lipid transport across the bacterial envelope

2019 ◽  
Author(s):  
Georgia L. Isom ◽  
Nicolas Coudray ◽  
Mark R. MacRae ◽  
Collin T. McManus ◽  
Damian C. Ekiert ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Lipid Transport ◽  
Transport Systems ◽  
Permeability Barrier ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
E Coli ◽  
Outer Membranes ◽  
Hydrophobic Tunnel ◽  
Outer Membrane Permeability

Gram-negative bacteria are surrounded by an outer membrane composed of phospholipids and lipopolysaccharide (LPS), which acts as a barrier to the environment and contributes to antibiotic resistance. While mechanisms of LPS transport have been well characterised, systems that translocate phospholipids across the periplasm, such as MCE (Mammalian Cell Entry) transport systems, are less well understood. Here we show that E. coli MCE protein LetB (formerly YebT), forms a ∼0.6 megadalton complex in the periplasm. Our cryo-EM structure reveals that LetB consists of a stack of seven modular rings, creating a long hydrophobic tunnel through the centre of the complex. LetB is sufficiently large to span the gap between the inner and outer membranes, and mutations that shorten the tunnel abolish function. Lipids bind inside the tunnel, suggesting that it functions as a pathway for lipid transport. Cryo-EM structures in the open and closed states reveal a dynamic tunnel lining, with implications for gating or substrate translocation. Together, our results support a model in which LetB establishes a physical link between the bacterial inner and outer membranes, and creates a hydrophobic pathway for the translocation of lipids across the periplasm, to maintain the integrity of the outer membrane permeability barrier.

scholarly journals Localization and Regulation of the T1 Unimolecular Spanin

2018 ◽  
Vol 92 (22) ◽  
Author(s):  
Rohit Kongari ◽  
Jeffrey Snowden ◽  
Joel D. Berry ◽  
Ry Young
Keyword(s):  
Membrane Fusion ◽  
Outer Membrane ◽  
Fusion Proteins ◽  
Transmembrane Domain ◽  
Time Lapse ◽  
Negative Regulator ◽  
Viral Fusion ◽  
Outer Membranes ◽  
Two Component ◽  
Membrane Fusion Proteins

ABSTRACTSpanins are bacteriophage lysis proteins responsible for disruption of the outer membrane, the final step of Gram-negative host lysis. The absence of spanins results in a terminal phenotype of fragile spherical cells. The phage T1 employs a unimolecular spanin gp11that has an N-terminal lipoylation signal and a C-terminal transmembrane domain. Upon maturation and localization, gp11ends up as an outer membrane lipoprotein with a C-terminal transmembrane domain embedded in the inner membrane, thus connecting both membranes as a covalent polypeptide chain. Unlike the two-component spanins encoded by most of the other phages, including lambda, the unimolecular spanins have not been studied extensively. In this work, we show that the gp11mutants lacking either membrane localization signal were nonfunctional and conferred a partially dominant phenotype. Translation from internal start sites within the gp11coding sequence generated a shorter product which exhibited a negative regulatory effect on gp11function. Fluorescence spectroscopy time-lapse videos of gp11-GFP expression showed gp11accumulated in distinct punctate foci, suggesting localized clusters assembled within the peptidoglycan meshwork. In addition, gp11was shown to mediate lysis in the absence of holin and endolysin function when peptidoglycan density was depleted by starvation for murein precursors. This result indicates that the peptidoglycan is a negative regulator of gp11function. This supports a model in which gp11acts by fusing the inner and outer membranes, a mode of action analogous to but mechanistically distinct from that proposed for the two-component spanin systems.IMPORTANCESpanins have been proposed to fuse the cytoplasmic and outer membranes during phage lysis. Recent work with the lambda spanins Rz-Rz1, which are similar to class I viral fusion proteins, has shed light on the functional domains and requirements for two-component spanin function. Here we report, for the first time, a genetic and biochemical approach to characterize unimolecular spanins, which are structurally and mechanistically different from two-component spanins. Considering similar predicted secondary structures within the ectodomains, unimolecular spanins can be regarded as a prokaryotic version of type II viral membrane fusion proteins. This study not only adds to our understanding of regulation of phage lysis at various levels but also provides a prokaryotic genetically tractable platform for interrogating class II-like membrane fusion proteins.

scholarly journals Assembly and Channel Opening of Outer Membrane Protein in Tripartite Drug Efflux Pumps of Gram-negative Bacteria

2012 ◽  
Vol 287 (15) ◽  
pp. 11740-11750 ◽  
Author(s):  
Yongbin Xu ◽  
Arne Moeller ◽  
So-Young Jun ◽  
Minho Le ◽  
Bo-Young Yoon ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Fusion Protein ◽  
Membrane Fusion ◽  
Outer Membrane ◽  
Outer Membrane Protein ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Membrane Fusion Protein ◽  
Docking Model ◽  
Channel Opening

Gram-negative bacteria are capable of expelling diverse xenobiotic substances from within the cell by use of three-component efflux pumps in which the energy-activated inner membrane transporter is connected to the outer membrane channel protein via the membrane fusion protein. In this work, we describe the crystal structure of the membrane fusion protein MexA from the Pseudomonas aeruginosa MexAB-OprM pump in the hexameric ring arrangement. Electron microscopy study on the chimeric complex of MexA and the outer membrane protein OprM reveals that MexA makes a tip-to-tip interaction with OprM, which suggests a docking model for MexA and OprM. This docking model agrees well with genetic results and depicts detailed interactions. Opening of the OprM channel is accompanied by the simultaneous exposure of a protein structure resembling a six-bladed cogwheel, which intermeshes with the complementary cogwheel structure in the MexA hexamer. Taken together, we suggest an assembly and channel opening model for the MexAB-OprM pump. This study provides a better understanding of multidrug resistance in Gram-negative bacteria.

scholarly journals Opening the Channel: the Two Functional Interfaces of Pseudomonas aeruginosa OpmH with the Triclosan Efflux Pump TriABC

2016 ◽  
Vol 198 (23) ◽  
pp. 3176-3185 ◽  
Author(s):  
Abigail T. Ntreh ◽  
Jon W. Weeks ◽  
Logan M. Nickels ◽  
Helen I. Zgurskaya
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Membrane Fusion ◽  
Outer Membrane ◽  
Fusion Proteins ◽  
Efflux Pump ◽  
Cell Envelope ◽  
Functional Integration ◽  
Content Type ◽  
Membrane Fusion Proteins ◽  
Stimulation Of

ABSTRACTTriABC-OpmH is an efflux pump fromPseudomonas aeruginosawith an unusual substrate specificity and protein composition. When overexpressed, this pump confers a high level of resistance to the biocide triclosan and the detergent SDS, which are commonly used in combinations for antimicrobial treatments. This activity requires an RND transporter (TriC), an outer membrane channel (OpmH), and two periplasmic membrane fusion proteins (TriA and TriB) with nonequivalent functions. In the active complex, TriA is responsible for the recruitment of OpmH, while TriB is responsible for stimulation of the transporter TriC. Here, we used the functional and structural differences between the two membrane fusion proteins to link their functional roles to specific interactions with OpmH. Our results provide evidence that the TriB-dependent stimulation of the TriC transporter is coupled to opening of the OpmH aperture through binding to the interprotomer groove of OpmH.IMPORTANCEMultidrug efflux transporters are important contributors to intrinsic and acquired antibiotic resistance in clinics. In Gram-negative bacteria, these transporters have a characteristic tripartite architecture spanning the entire two-membrane cell envelope. How such complexes are assembled and how the reactions separated in two different membranes are coupled to provide efficient efflux of various compounds across the cell envelope remain unclear. This study addressed these questions, and the results suggest a mechanism for functional integration of drug efflux by the inner membrane transporter and opening of the channel for transport across the outer membrane.

scholarly journals Correct Sorting of Lipoproteins into the Inner and Outer Membranes ofPseudomonas aeruginosaby theEscherichia coliLolCDE Transport System

mBio ◽  
2019 ◽  
Vol 10 (2) ◽  
Author(s):  
Christian Lorenz ◽  
Thomas J. Dougherty ◽  
Stephen Lory
Keyword(s):  
Escherichia Coli ◽  
Pseudomonas Aeruginosa ◽  
Outer Membrane ◽  
Transport Systems ◽  
Gram Negative Bacteria ◽  
Inner Membrane ◽  
Gram Negative ◽  
Content Type ◽  
E Coli ◽  
Outer Membranes

ABSTRACTBiogenesis of the outer membrane of Gram-negative bacteria depends on dedicated macromolecular transport systems. The LolABCDE proteins make up the machinery for lipoprotein trafficking from the inner membrane (IM) across the periplasm to the outer membrane (OM). The Lol apparatus is additionally responsible for differentiating OM lipoproteins from those for the IM. InEnterobacteriaceae, a default sorting mechanism has been proposed whereby an aspartic acid at position +2 of the mature lipoproteins prevents Lol recognition and leads to their IM retention. In other bacteria, the conservation of sequences immediately following the acylated cysteine is variable. Here we show that inPseudomonas aeruginosa, the three essential Lol proteins (LolCDE) can be replaced with those fromEscherichia coli. TheP. aeruginosalipoproteins MexA, OprM, PscJ, and FlgH, with different sequences at their N termini, were correctly sorted by either theE. coliorP. aeruginosaLolCDE. We further demonstrate that an inhibitor ofE. coliLolCDE is active againstP. aeruginosaonly when expressing theE. coliorthologues. Our work shows that Lol proteins recognize a wide range of signals, consisting of an acylated cysteine and a specific conformation of the adjacent domain, determining IM retention or transport to the OM.IMPORTANCEGram-negative bacteria build their outer membranes (OM) from components that are initially located in the inner membrane (IM). A fraction of lipoproteins is transferred to the OM by the transport machinery consisting of LolABCDE proteins. Our work demonstrates that the LolCDE complexes of the transport pathways ofEscherichia coliandPseudomonas aeruginosaare interchangeable, with theE. coliorthologues correctly sorting theP. aeruginosalipoproteins while retaining their sensitivity to a small-molecule inhibitor. These findings question the nature of IM retention signals, identified inE. colias aspartate at position +2 of mature lipoproteins. We propose an alternative model for the sorting of IM and OM lipoproteins based on their relative affinities for the IM and the ability of the promiscuous sorting machinery to deliver lipoproteins to their functional sites in the OM.

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