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Gloria Andolina, László-Csaba Bencze, Katja Zerbe, Maik Müller, Jessica Steinmann, Harsha Kocherla, Milon Mondal, Jens Sobek, Kerstin Moehle, Goran Malojčić, Bernd Wollscheid, John A Robinson
The outer membrane (OM) in Gram-negative bacteria is an asymmetric bilayer with mostly lipopolysaccharide (LPS) molecules in the outer leaflet. During OM biogenesis, new LPS molecules are transported from their site of assembly on the inner membrane to the OM by seven LPS transport proteins (LptA-G). The complex formed between the integral β-barrel OM protein LptD and the lipoprotein LptE is responsible for transporting LPS from the periplasmic side of the OM to its final location on the cell surface. Because of its essential function in many Gram-negative bacteria, the LPS transport pathway is an interesting target for the development of new antibiotics...
March 16, 2018: ACS Chemical Biology
Ryoji Miyazaki, Naomi Myougo, Hiroyuki Mori, Yoshinori Akiyama
Many proteins form multimeric complexes that play crucial roles in various cellular processes. Studying how proteins are correctly folded and assembled into such complexes in a living cell is important for understanding the physiological roles and the qualitative and quantitative regulation of the complex. However, few methods are suitable for analyzing these rapidly occurring processes. Site-directed in vivo photo-cross-linking is an elegant technique that enables analysis of protein-protein interactions in living cells with high spatial resolution...
January 12, 2018: Journal of Biological Chemistry
Istvan Botos, Nicholas Noinaj, Susan K Buchanan
The bacterial outer membrane contains phospholipids in the inner leaflet and lipopolysaccharide (LPS) in the outer leaflet. Both proteins and LPS must be frequently inserted into the outer membrane to preserve its integrity. The protein complex that inserts LPS into the outer membrane is called LptDE, and consists of an integral membrane protein, LptD, with a separate globular lipoprotein, LptE, inserted in the barrel lumen. The protein complex that inserts newly synthesized outer-membrane proteins (OMPs) into the outer membrane is called the BAM complex, and consists of an integral membrane protein, BamA, plus four lipoproteins, BamB, C, D and E...
August 5, 2017: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
Jianqiang Liang, Mingzhe Zhang, Mingmei Lu, Zhefei Li, Xihui Shen, Minxia Chou, Gehong Wei
Random mutagenesis in a symbiotic nitrogen-fixing Bradyrhizobium liaoningense CCNWSX0360 (Bln0360) using Tn5 identified five copper (Cu) resistance-related genes. They were functionally sorted into three groups: transmembrane transport (cueA and tolC); oxidation (copA); and protection of the membrane barrier (lptE and ctpA). The gene cueA, together with the upstream csoR (Cu-sensitive operon repressor), constituted a csoR-cueA divergon which plays a crucial role in Cu homeostasis. Deletion of cueA decreased the Cu tolerance of cells, and complementation of this mutant restored comparable Cu resistance to that of the wild-type...
October 11, 2016: Scientific Reports
James Lee, Mingyu Xue, Joseph S Wzorek, Tao Wu, Marcin Grabowicz, Luisa S Gronenberg, Holly A Sutterlin, Rebecca M Davis, Natividad Ruiz, Thomas J Silhavy, Daniel E Kahne
The assembly of β-barrel proteins into membranes is mediated by an evolutionarily conserved machine. This process is poorly understood because no stable partially folded barrel substrates have been characterized. Here, we slowed the folding of the Escherichia coli β-barrel protein, LptD, with its lipoprotein plug, LptE. We identified a late-stage intermediate in which LptD is folded around LptE, and both components interact with the two essential β-barrel assembly machine (Bam) components, BamA and BamD...
August 2, 2016: Proceedings of the National Academy of Sciences of the United States of America
Kerstin Moehle, Harsha Kocherla, Bernadett Bacsa, Simon Jurt, Katja Zerbe, John A Robinson, Oliver Zerbe
LptE is an outer membrane (OM) lipoprotein found in Gram-negative bacteria, where it forms a complex with the β-barrel lipopolysaccharide (LPS) transporter LptD. The LptD/E complex plays a key role in OM biogenesis, by translocating newly synthesized LPS molecules from the periplasm into the external leaflet of the asymmetric OM during cell growth. The LptD/E complex in Pseudomonas aeruginosa (Pa) is a target for macrocyclic β-hairpin-shaped peptidomimetic antibiotics, which inhibit the transport of LPS to the cell surface...
May 31, 2016: Biochemistry
YingWang Ye, Jina Gao, Rui Jiao, Hui Li, Qingping Wu, Jumei Zhang, Xian Zhong
Cronobacter sakazakii is an opportunistic foodborne pathogen and the virulence differences were previously documented. However, information about membranous proteins involved in virulence differences was not available. In this study, virulent characterization such as biofilm formation and flagella motility between virulent C. sakazakii isolate G362 and attenuated L3101 were determined. Then, two-dimensional gel electrophoresis (2-DE) technology was used to preliminarily reveal differential expression of membranous proteins between G362 and L3101...
2015: Frontiers in Microbiology
S Uemoto, K Ozawa, T Kaido, A Mori, Y Fujimoto
Our previous work revealed that the recipients with the highest pre-existing numbers of CD8(+) effector T cells (TE ) [hyperparathyroidism (HPT)E recipients] occupied approximately 30% of adult transplant recipients performed in our hospital. HPTE recipients demonstrated very poor clinical outcome compared with the remaining 70% of recipients with the lowest pre-existing TE (LPTE recipient). This study aimed to clarify the best combined immunosuppressive regimen related to function of cytotoxic T lymphocytes (CTLs) for HPTE recipients...
April 2016: Clinical and Experimental Immunology
Shuai Qiao, Qingshan Luo, Yan Zhao, Xuejun Cai Zhang, Yihua Huang
One of the fundamental properties of biological membranes is the asymmetric distribution of membrane lipids. In Gram-negative bacteria, the outer leaflet of the outer membrane is composed predominantly of lipopolysaccharides (LPS). The export of LPS requires seven essential lipopolysaccharide transport (Lpt) proteins to move LPS from the inner membrane, through the periplasm to the surface. Of the seven Lpt proteins, the LptD-LptE complex is responsible for inserting LPS into the external leaflet of the outer membrane...
July 3, 2014: Nature
Haohao Dong, Quanju Xiang, Yinghong Gu, Zhongshan Wang, Neil G Paterson, Phillip J Stansfeld, Chuan He, Yizheng Zhang, Wenjian Wang, Changjiang Dong
Lipopolysaccharide (LPS) is essential for most Gram-negative bacteria and has crucial roles in protection of the bacteria from harsh environments and toxic compounds, including antibiotics. Seven LPS transport proteins (that is, LptA-LptG) form a trans-envelope protein complex responsible for the transport of LPS from the inner membrane to the outer membrane, the mechanism for which is poorly understood. Here we report the first crystal structure of the unique integral membrane LPS translocon LptD-LptE complex...
July 3, 2014: Nature
Goran Malojčić, Dorothee Andres, Marcin Grabowicz, Alexander H George, Natividad Ruiz, Thomas J Silhavy, Daniel Kahne
The assembly of lipopolysaccharide (LPS) on the surface of Gram-negative bacterial cells is essential for their viability and is achieved by the seven-protein LPS transport (Lpt) pathway. The outer membrane (OM) lipoprotein LptE and the β-barrel membrane protein LptD form a complex that assembles LPS into the outer leaflet of the OM. We report a crystal structure of the Escherichia coli OM lipoprotein LptE at 2.34 Å. The structure reveals homology to eukaryotic LPS-binding proteins and allowed for the prediction of an LPS-binding site, which was confirmed by genetic and biophysical experiments...
July 1, 2014: Proceedings of the National Academy of Sciences of the United States of America
Marcin Grabowicz, Jennifer Yeh, Thomas J Silhavy
Lipopolysaccharide (LPS) is the major outer leaflet constituent of the Gram-negative outer membrane (OM) bilayer. A bipartite protein complex of LptD and LptE assembles LPS into the OM. It has been established that LptE assists folding and assembly of its β-barrel partner LptD, yet reported biochemical evidence suggested additional LptE functions. Here, we isolated dominant negative lptE mutations, seeking to inform these functions. The lptE14 mutation increased OM permeability to erythromycin, even when the wild-type lptE gene was present...
March 2013: Journal of Bacteriology
Shu-Sin Chng, Mingyu Xue, Ronald A Garner, Hiroshi Kadokura, Dana Boyd, Jonathan Beckwith, Daniel Kahne
The presence of lipopolysaccharide (LPS) on the cell surface of Gram-negative bacteria is critical for viability. A conserved β-barrel membrane protein LptD (lipopolysaccharide transport protein D) translocates LPS from the periplasm across the outer membrane (OM). In Escherichia coli, this protein contains two disulfide bonds and forms the OM LPS translocon with the lipoprotein LptE. Here, we identified seven in vivo states on the oxidative-folding pathway of LptD. Proper assembly involved a nonfunctional intermediate containing non-native disulfides...
September 28, 2012: Science
Martina Werneburg, Katja Zerbe, Mario Juhas, Laurent Bigler, Urs Stalder, Andres Kaech, Urs Ziegler, Daniel Obrecht, Leo Eberl, John A Robinson
The asymmetric outer membrane (OM) of Gram-negative bacteria contains lipopolysaccharide (LPS) in the outer leaflet and phospholipid in the inner leaflet. During OM biogenesis, LPS is transported from the periplasm into the outer leaflet by a complex comprising the OM proteins LptD and LptE. Recently, a new family of macrocyclic peptidomimetic antibiotics that interact with LptD of the opportunistic human pathogen Pseudomonas aeruginosa was discovered. Here we provide evidence that the peptidomimetics inhibit the LPS transport function of LptD...
August 13, 2012: Chembiochem: a European Journal of Chemical Biology
Martine P Bos, Jan Tommassen
The biosynthesis of lipopolysaccharide (LPS) in gram-negative bacteria is well understood, in contrast to the transport to its destination, the outer leaflet of the outer membrane. In Escherichia coli, synthesis and transport of LPS are essential processes. Neisseria meningitidis, conversely, can survive without LPS and tolerates inactivation of genes involved in LPS synthesis and transport. Here, we analyzed whether the LptA, LptB, LptC, LptE, LptF, and LptG proteins, recently implicated in LPS transport in E...
August 19, 2011: Journal of Biological Chemistry
Gitanjali Chimalakonda, Natividad Ruiz, Shu-Sin Chng, Ronald A Garner, Daniel Kahne, Thomas J Silhavy
Most Gram-negative bacteria contain lipopolysaccharide (LPS), a glucosamine-based phospholipid, in the outer leaflet of the outer membrane (OM). LPS is unique to the bacterial OM and, in most cases, essential for cell viability. Transport of LPS from its site of synthesis to the cell surface requires eight essential proteins, MsbA and LptABCDEFG. Although the key players have been identified, the mechanism of LPS transport and assembly is not clear. The stable LptD/E complex is present at the OM and functions in the final stages of LPS assembly...
February 8, 2011: Proceedings of the National Academy of Sciences of the United States of America
Elizaveta Freinkman, Shu-Sin Chng, Daniel Kahne
The cell surfaces of Gram-negative bacteria are composed of lipopolysaccharide (LPS). This glycolipid is found exclusively in the outer leaflet of the asymmetric outer membrane (OM), where it forms a barrier to the entry of toxic hydrophobic molecules into the cell. LPS typically contains six fatty acyl chains and up to several hundred sugar residues. It is biosynthesized in the cytosol and must then be transported across two membranes and an aqueous intermembrane space to the cell surface. These processes are required for the viability of most Gram-negative organisms...
February 8, 2011: Proceedings of the National Academy of Sciences of the United States of America
Alexandra Bowyer, Jason Baardsnes, Eunice Ajamian, Linhua Zhang, Miroslaw Cygler
The lipopolysaccharide transport system (Lpt) in Gram-negative bacteria is responsible for transporting lipopolysaccharide (LPS) from the cytoplasmic surface of the inner membrane, where it is assembled, across the inner membrane, periplasm and outer membrane, to the surface where it is then inserted in the outer leaflet of the asymmetric lipid bilayer. The Lpt system consists of seven known LPS transport proteins (LptA-G) spanning from the cytoplasm to the cell surface. We have shown that the periplasmic component, LptA is able to form a stable complex with the inner membrane anchored LptC but does not interact with the outer membrane anchored LptE...
January 28, 2011: Biochemical and Biophysical Research Communications
Natividad Ruiz, Shu-Sin Chng, Annie Hiniker, Daniel Kahne, Thomas J Silhavy
The Gram-negative bacterial envelope is bounded by two membranes. Disulfide bond formation and isomerization in this oxidizing environment are catalyzed by DsbA and DsbC, respectively. It remains unknown when and how the Dsb proteins participate in the biogenesis of outer membrane proteins, which are transported across the cell envelope after their synthesis. The Escherichia coli protein LptD is an integral outer membrane protein that forms an essential complex with the lipoprotein LptE. We show that oxidation of LptD is not required for the formation of the LptD/E complex but it is essential for function...
July 6, 2010: Proceedings of the National Academy of Sciences of the United States of America
Shu-Sin Chng, Natividad Ruiz, Gitanjali Chimalakonda, Thomas J Silhavy, Daniel Kahne
Lipopolysaccharide (LPS) is the major glycolipid that is present in the outer membranes (OMs) of most Gram-negative bacteria. LPS molecules are assembled with divalent metal cations in the outer leaflet of the OM to form an impervious layer that prevents toxic compounds from entering the cell. For most Gram-negative bacteria, LPS is essential for growth. In Escherichia coli, eight essential proteins have been identified to function in the proper assembly of LPS following its biosynthesis. This assembly process involves release of LPS from the inner membrane (IM), transport across the periplasm, and insertion into the outer leaflet of the OM...
March 23, 2010: Proceedings of the National Academy of Sciences of the United States of America
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