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Orfanoudaki G, Markaki M, Chatzi K, Tsamardinos I, Economou A. MatureP: prediction of secreted proteins with exclusive information from their mature regions. Sci Rep 2017; 7:3263. [PMID: 28607462 PMCID: PMC5468347 DOI: 10.1038/s41598-017-03557-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 04/28/2017] [Indexed: 11/09/2022] Open
Abstract
More than a third of the cellular proteome is non-cytoplasmic. Most secretory proteins use the Sec system for export and are targeted to membranes using signal peptides and mature domains. To specifically analyze bacterial mature domain features, we developed MatureP, a classifier that predicts secretory sequences through features exclusively computed from their mature domains. MatureP was trained using Just Add Data Bio, an automated machine learning tool. Mature domains are predicted efficiently with ~92% success, as measured by the Area Under the Receiver Operating Characteristic Curve (AUC). Predictions were validated using experimental datasets of mutated secretory proteins. The features selected by MatureP reveal prominent differences in amino acid content between secreted and cytoplasmic proteins. Amino-terminal mature domain sequences have enhanced disorder, more hydroxyl and polar residues and less hydrophobics. Cytoplasmic proteins have prominent amino-terminal hydrophobic stretches and charged regions downstream. Presumably, secretory mature domains comprise a distinct protein class. They balance properties that promote the necessary flexibility required for the maintenance of non-folded states during targeting and secretion with the ability of post-secretion folding. These findings provide novel insight in protein trafficking, sorting and folding mechanisms and may benefit protein secretion biotechnology.
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Affiliation(s)
- Georgia Orfanoudaki
- Institute of Molecular Biology and Biotechnology-FORTH and Department of Biology-University of Crete, PO Box 1385, Heraklion, Crete, Greece
| | - Maria Markaki
- Computer Science Department, University of Crete, Heraklion, Greece
| | - Katerina Chatzi
- KU Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, B-3000, Leuven, Belgium
| | - Ioannis Tsamardinos
- Computer Science Department, University of Crete, Heraklion, Greece.,Gnosis Data Analysis PC, Heraklion, Greece
| | - Anastassios Economou
- Institute of Molecular Biology and Biotechnology-FORTH and Department of Biology-University of Crete, PO Box 1385, Heraklion, Crete, Greece. .,KU Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, B-3000, Leuven, Belgium.
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52
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Hooda Y, Lai CCL, Moraes TF. Identification of a Large Family of Slam-Dependent Surface Lipoproteins in Gram-Negative Bacteria. Front Cell Infect Microbiol 2017; 7:207. [PMID: 28620585 PMCID: PMC5449769 DOI: 10.3389/fcimb.2017.00207] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 05/09/2017] [Indexed: 02/01/2023] Open
Abstract
The surfaces of many Gram-negative bacteria are decorated with soluble proteins anchored to the outer membrane via an acylated N-terminus; these proteins are referred to as surface lipoproteins or SLPs. In Neisseria meningitidis, SLPs such as transferrin-binding protein B (TbpB) and factor-H binding protein (fHbp) are essential for host colonization and infection because of their essential roles in iron acquisition and immune evasion, respectively. Recently, we identified a family of outer membrane proteins called Slam (Surface lipoprotein assembly modulator) that are essential for surface display of neisserial SLPs. In the present study, we performed a bioinformatics analysis to identify 832 Slam related sequences in 638 Gram-negative bacterial species. The list included several known human pathogens, many of which were not previously reported to possess SLPs. Hypothesizing that genes encoding SLP substrates of Slams may be present in the same gene cluster as the Slam genes, we manually curated neighboring genes for 353 putative Slam homologs. From our analysis, we found that 185 (~52%) of the 353 putative Slam homologs are located adjacent to genes that encode a protein with an N-terminal lipobox motif. This list included genes encoding previously reported SLPs in Haemophilus influenzae and Moraxella catarrhalis, for which we were able to show that the neighboring Slams are necessary and sufficient to display these lipoproteins on the surface of Escherichia coli. To further verify the authenticity of the list of predicted SLPs, we tested the surface display of one such Slam-adjacent protein from Pasteurella multocida, a zoonotic pathogen. A robust Slam-dependent display of the P. multocida protein was observed in the E. coli translocation assay indicating that the protein is a Slam-dependent SLP. Based on multiple sequence alignments and domain annotations, we found that an eight-stranded beta-barrel domain is common to all the predicted Slam-dependent SLPs. These findings suggest that SLPs with a TbpB-like fold are found widely in Proteobacteria where they exist with their interaction partner Slam. In the future, SLPs found in pathogenic bacteria can be investigated for their role in virulence and may also serve as candidates for vaccine development.
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Affiliation(s)
- Yogesh Hooda
- Department of Biochemistry, University of TorontoToronto, ON, Canada
| | - Christine C L Lai
- Department of Biochemistry, University of TorontoToronto, ON, Canada
| | - Trevor F Moraes
- Department of Biochemistry, University of TorontoToronto, ON, Canada
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Gunasinghe SD, Webb CT, Elgass KD, Hay ID, Lithgow T. Super-Resolution Imaging of Protein Secretion Systems and the Cell Surface of Gram-Negative Bacteria. Front Cell Infect Microbiol 2017; 7:220. [PMID: 28611954 PMCID: PMC5447050 DOI: 10.3389/fcimb.2017.00220] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 05/12/2017] [Indexed: 12/28/2022] Open
Abstract
Gram-negative bacteria have a highly evolved cell wall with two membranes composed of complex arrays of integral and peripheral proteins, as well as phospholipids and glycolipids. In order to sense changes in, respond to, and exploit their environmental niches, bacteria rely on structures assembled into or onto the outer membrane. Protein secretion across the cell wall is a key process in virulence and other fundamental aspects of bacterial cell biology. The final stage of protein secretion in Gram-negative bacteria, translocation across the outer membrane, is energetically challenging so sophisticated nanomachines have evolved to meet this challenge. Advances in fluorescence microscopy now allow for the direct visualization of the protein secretion process, detailing the dynamics of (i) outer membrane biogenesis and the assembly of protein secretion systems into the outer membrane, (ii) the spatial distribution of these and other membrane proteins on the bacterial cell surface, and (iii) translocation of effector proteins, toxins and enzymes by these protein secretion systems. Here we review the frontier research imaging the process of secretion, particularly new studies that are applying various modes of super-resolution microscopy.
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Affiliation(s)
- Sachith D Gunasinghe
- Infection and Immunity Program, Department of Microbiology, Biomedicine Discovery Institute, Monash UniversityClayton, VIC, Australia
| | - Chaille T Webb
- Infection and Immunity Program, Department of Microbiology, Biomedicine Discovery Institute, Monash UniversityClayton, VIC, Australia
| | | | - Iain D Hay
- Infection and Immunity Program, Department of Microbiology, Biomedicine Discovery Institute, Monash UniversityClayton, VIC, Australia
| | - Trevor Lithgow
- Infection and Immunity Program, Department of Microbiology, Biomedicine Discovery Institute, Monash UniversityClayton, VIC, Australia
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54
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Zhang S, He D, Lin Z, Yang Y, Song H, Chen PR. Conditional Chaperone-Client Interactions Revealed by Genetically Encoded Photo-cross-linkers. Acc Chem Res 2017; 50:1184-1192. [PMID: 28467057 DOI: 10.1021/acs.accounts.6b00647] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The cell envelope is an integral and essential component of Gram-negative bacteria. As the front line during host-pathogen interactions, it is directly challenged by host immune responses as well as other harsh extracellular stimuli. The high permeability of the outer-membrane and the lack of ATP energy system render it difficult to maintain important biological activities within the periplasmic space under stress conditions. The HdeA/B chaperone machinery is the only known acid resistant system found in bacterial periplasm, enabling enteric pathogens to survive through the highly acidic human stomach and establish infections in the intestine. These two homologous chaperones belong to a fast growing family of conditionally disordered chaperones that conditionally lose their well-defined three-dimensional structures to exert biological activities. Upon losing ordered structures, these proteins commit promiscuous binding of diverse clients in response to environmental stimulation. For example, HdeA and HdeB are well-folded inactive dimers at neutral pH but become partially unfolded to protect a wide array of acid-denatured proteins upon acid stress. Whether these conditionally disordered chaperones possess client specificities remains unclear. This is in part due to the lack of efficient tools to investigate such versatile and heterogeneous protein-protein interactions under living conditions. Genetically encoded protein photo-cross-linkers have offered a powerful strategy to capture protein-protein interactions, showing great potential in profiling protein interaction networks, mapping binding interfaces, and probing dynamic changes in both physiological and pathological settings. Despite great success, photo-cross-linkers that can simultaneously capture the promiscuous binding partners and directly identify the interaction interfaces remain technically challenging. Furthermore, methods for side-by-side profiling and comparing the condition-dependent client pools from two homologous chaperones are lacking. Herein, we introduce our recent efforts in developing a panel of versatile genetically encoded photo-cross-linkers to study the disorder-mediated chaperone-client interactions in living cells. In particular, we have developed a series of proteomic-based strategies relying on these new photo-cross-linkers to systematically compare the client profiles of HdeA and HdeB, as well as to map their interaction interfaces. These studies revealed the mode-of-action, particularly the client specificity, of these two conditionally disordered chaperones. In the end, some recent elegant work from other groups that applied the genetically encoded photo-cross-linking strategy to illuminate important protein-protein interactions within bacterial cell envelope is also discussed.
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Affiliation(s)
- Shuai Zhang
- Beijing National
Laboratory for Molecular Sciences, Synthetic and Functional Biomolecules
Center, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Dan He
- Beijing National
Laboratory for Molecular Sciences, Synthetic and Functional Biomolecules
Center, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Zhi Lin
- Beijing National
Laboratory for Molecular Sciences, Synthetic and Functional Biomolecules
Center, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Yi Yang
- Beijing National
Laboratory for Molecular Sciences, Synthetic and Functional Biomolecules
Center, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Haiping Song
- Beijing National
Laboratory for Molecular Sciences, Synthetic and Functional Biomolecules
Center, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Peng R. Chen
- Beijing National
Laboratory for Molecular Sciences, Synthetic and Functional Biomolecules
Center, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
- Academy for Advanced Interdisciplinary Studies, Peking-Tsinghua Center for Life Sciences, Beijing 100871, China
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Chatzi KE, Sardis MF, Tsirigotaki A, Koukaki M, Šoštarić N, Konijnenberg A, Sobott F, Kalodimos CG, Karamanou S, Economou A. Preprotein mature domains contain translocase targeting signals that are essential for secretion. J Cell Biol 2017; 216:1357-1369. [PMID: 28404644 PMCID: PMC5412566 DOI: 10.1083/jcb.201609022] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Revised: 10/07/2016] [Accepted: 02/23/2017] [Indexed: 11/22/2022] Open
Abstract
Secretory proteins are only temporary cytoplasmic residents. They are typically synthesized as preproteins, carrying signal peptides N-terminally fused to their mature domains. In bacteria secretion largely occurs posttranslationally through the membrane-embedded SecA-SecYEG translocase. Upon crossing the plasma membrane, signal peptides are cleaved off and mature domains reach their destinations and fold. Targeting to the translocase is mediated by signal peptides. The role of mature domains in targeting and secretion is unclear. We now reveal that mature domains harbor their own independent targeting signals (mature domain targeting signals [MTSs]). These are multiple, degenerate, interchangeable, linear or 3D hydrophobic stretches that become available because of the unstructured states of targeting-competent preproteins. Their receptor site on the cytoplasmic face of the SecYEG-bound SecA is also of hydrophobic nature and is located adjacent to the signal peptide cleft. Both the preprotein MTSs and their receptor site on SecA are essential for protein secretion. Evidently, mature domains have their own previously unsuspected distinct roles in preprotein targeting and secretion.
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Affiliation(s)
- Katerina E Chatzi
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
| | - Marios Frantzeskos Sardis
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
| | - Alexandra Tsirigotaki
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
| | - Marina Koukaki
- Institute of Molecular Biology and Biotechnology FoRTH, Iraklio, 71110 Crete, Greece
| | - Nikolina Šoštarić
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
| | - Albert Konijnenberg
- Biomolecular and Analytical Mass Spectrometry Group, Department of Chemistry, University of Antwerp, 2000 Antwerp, Belgium
| | - Frank Sobott
- Biomolecular and Analytical Mass Spectrometry Group, Department of Chemistry, University of Antwerp, 2000 Antwerp, Belgium
| | - Charalampos G Kalodimos
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455
| | - Spyridoula Karamanou
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
| | - Anastassios Economou
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, Katholieke Universiteit Leuven, 3000 Leuven, Belgium .,Institute of Molecular Biology and Biotechnology FoRTH, Iraklio, 71110 Crete, Greece
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Identification of specific posttranslational O-mycoloylations mediating protein targeting to the mycomembrane. Proc Natl Acad Sci U S A 2017; 114:4231-4236. [PMID: 28373551 DOI: 10.1073/pnas.1617888114] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The outer membranes (OMs) of members of the Corynebacteriales bacterial order, also called mycomembranes, harbor mycolic acids and unusual outer membrane proteins (OMPs), including those with α-helical structure. The signals that allow precursors of such proteins to be targeted to the mycomembrane remain uncharacterized. We report here the molecular features responsible for OMP targeting to the mycomembrane of Corynebacterium glutamicum, a nonpathogenic member of the Corynebacteriales order. To better understand the mechanisms by which OMP precursors were sorted in C. glutamicum, we first investigated the partitioning of endogenous and recombinant PorA, PorH, PorB, and PorC between bacterial compartments and showed that they were both imported into the mycomembrane and secreted into the extracellular medium. A detailed investigation of cell extracts and purified proteins by top-down MS, NMR spectroscopy, and site-directed mutagenesis revealed specific and well-conserved posttranslational modifications (PTMs), including O-mycoloylation, pyroglutamylation, and N-formylation, for mycomembrane-associated and -secreted OMPs. PTM site sequence analysis from C. glutamicum OMP and other O-acylated proteins in bacteria and eukaryotes revealed specific patterns. Furthermore, we found that such modifications were essential for targeting to the mycomembrane and sufficient for OMP assembly into mycolic acid-containing lipid bilayers. Collectively, it seems that these PTMs have evolved in the Corynebacteriales order and beyond to guide membrane proteins toward a specific cell compartment.
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Abstract
In Gram-negative bacteria, the biogenesis of β-barrel outer membrane proteins (OMPs) is mediated by the β-barrel assembly machinery (BAM) complex. During the past decade, structural and functional studies have collectively contributed to advancing our understanding of the structure and function of the BAM complex; however, the exact mechanism that is involved remains elusive. In this Progress article, we discuss recent structural studies that have revealed that the accessory proteins may regulate essential unprecedented conformational changes in the core component BamA during function. We also detail the mechanistic insights that have been gained from structural data, mutagenesis studies and molecular dynamics simulations, and explore two emerging models for the BAM-mediated biogenesis of OMPs in bacteria.
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Affiliation(s)
- Nicholas Noinaj
- Markey Center for Structural Biology, Department of Biological Sciences and the Purdue Institute for Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, Indiana 47907, USA
| | - James C Gumbart
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - Susan K Buchanan
- National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892, USA
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60
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Stubenrauch C, Grinter R, Lithgow T. The modular nature of the β-barrel assembly machinery, illustrated in Borrelia burgdorferi. Mol Microbiol 2016; 102:753-756. [PMID: 27618357 DOI: 10.1111/mmi.13527] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/07/2016] [Indexed: 12/13/2022]
Abstract
Diderm bacteria have an outer membrane that provides defense against environmental factors including antibiotics. Understanding the process of outer membrane biogenesis is, therefore, of critical importance in order to envisage new treatments of these bacterial pathogens. Borrelia burgdorferi is the pathogen responsible for Lyme disease. Its outer membrane contains integral, β-barrel proteins as well as swathes of externally exposed lipoproteins. Previous work has demonstrated that the β-barrel assembly machine (BAM complex) in B. burgdorferi and other Spirochetes shares several similarities with the BAM complex in other bacterial lineages, such as the Proteobacteria that includes Escherichia coli. However, Iqbal et al. () have identified the inner membrane protein TamB as a subunit of the BAM complex in Spirochetes. This latest study highlights the modular nature of the BAM complex, and suggests that in some bacterial lineages the BAM complex and translocation and assembly module (the TAM) function as a single unit.
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Affiliation(s)
- Christopher Stubenrauch
- Infection and Immunity Program, Biomedicine Discovery Institute and Department of Microbiology, Monash University, Melbourne, 3800, Australia
| | - Rhys Grinter
- Infection and Immunity Program, Biomedicine Discovery Institute and Department of Microbiology, Monash University, Melbourne, 3800, Australia
| | - Trevor Lithgow
- Infection and Immunity Program, Biomedicine Discovery Institute and Department of Microbiology, Monash University, Melbourne, 3800, Australia
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