51
|
Abstract
Pili are crucial virulence factors for many Gram-negative pathogens. These surface structures provide bacteria with a link to their external environments by enabling them to interact with, and attach to, host cells, other surfaces or each other, or by providing a conduit for secretion. Recent high-resolution structures of pilus filaments and the machineries that produce them, namely chaperone-usher pili, type IV pili, conjugative type IV secretion pili and type V pili, are beginning to explain some of the intriguing biological properties that pili exhibit, such as the ability of chaperone-usher pili and type IV pili to stretch in response to external forces. By contrast, conjugative pili provide a conduit for the exchange of genetic information, and recent high-resolution structures have revealed an integral association between the pilin subunit and a phospholipid molecule, which may facilitate DNA transport. In addition, progress in the area of cryo-electron tomography has provided a glimpse of the overall architecture of the type IV pilus machinery. In this Review, we examine recent advances in our structural understanding of various Gram-negative pilus systems and discuss their functional implications.
Collapse
|
52
|
Kessel A, Kolodny R, Ben-Tal N. Similarity between the Usher Plug and the Repeating Domain of an Ice-adhesin: Evolution via Surface Reshaping. Isr J Chem 2017. [DOI: 10.1002/ijch.201600133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Amit Kessel
- Department of Biochemistry and Molecular Biology; George S. Wise Faculty of Life Sciences; Tel Aviv University; Ramat Aviv 69978 Israel
| | - Rachel Kolodny
- Department of Computer Sciences; University of Haifa; Mount Carmel 3 1905 Israel
| | - Nir Ben-Tal
- Department of Biochemistry and Molecular Biology; George S. Wise Faculty of Life Sciences; Tel Aviv University; Ramat Aviv 69978 Israel
| |
Collapse
|
53
|
Phan TH, Ummels R, Bitter W, Houben ENG. Identification of a substrate domain that determines system specificity in mycobacterial type VII secretion systems. Sci Rep 2017; 7:42704. [PMID: 28205541 PMCID: PMC5311947 DOI: 10.1038/srep42704] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 01/13/2017] [Indexed: 12/31/2022] Open
Abstract
Type VII secretion (T7S) systems are specialized machineries used by mycobacterial pathogens to transport important virulence factors across their highly hydrophobic cell envelope. There are up to five mycobacterial T7S systems, named ESX-1 to ESX-5, at least three of which specifically secrete a different subset of substrates. The T7S substrates or substrate complexes are defined by the general secretion motif YxxxD/E. However this motif does not determine system specificity. Here, we show that the substrate domain recognized by the EspG chaperone is the determinant factor for this specificity. We first show that the introduction of point mutations into the EspG1-binding domain of the ESX-1 substrate pair PE35/PPE68_1 affects their secretion. Subsequently, we demonstrate that replacing this domain by the EspG5-binding domain of the ESX-5 substrate PPE18 resulted in EspG5 dependence and exclusive rerouting to the ESX-5 system. This rerouting of PE35/PPE68_1 to the ESX-5 system had a negative effect on the secretion of endogenous ESX-5 substrates.
Collapse
Affiliation(s)
- Trang H Phan
- Section Molecular Microbiology, Amsterdam Institute of Molecules, Medicines &Systems, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Roy Ummels
- Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, The Netherlands
| | - Wilbert Bitter
- Section Molecular Microbiology, Amsterdam Institute of Molecules, Medicines &Systems, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.,Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, The Netherlands
| | - Edith N G Houben
- Section Molecular Microbiology, Amsterdam Institute of Molecules, Medicines &Systems, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| |
Collapse
|
54
|
Kalas V, Pinkner JS, Hannan TJ, Hibbing ME, Dodson KW, Holehouse AS, Zhang H, Tolia NH, Gross ML, Pappu RV, Janetka J, Hultgren SJ. Evolutionary fine-tuning of conformational ensembles in FimH during host-pathogen interactions. SCIENCE ADVANCES 2017; 3:e1601944. [PMID: 28246638 PMCID: PMC5302871 DOI: 10.1126/sciadv.1601944] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Accepted: 01/25/2017] [Indexed: 05/05/2023]
Abstract
Positive selection in the two-domain type 1 pilus adhesin FimH enhances Escherichia coli fitness in urinary tract infection (UTI). We report a comprehensive atomic-level view of FimH in two-state conformational ensembles in solution, composed of one low-affinity tense (T) and multiple high-affinity relaxed (R) conformations. Positively selected residues allosterically modulate the equilibrium between these two conformational states, each of which engages mannose through distinct binding orientations. A FimH variant that only adopts the R state is severely attenuated early in a mouse model of uncomplicated UTI but is proficient at colonizing catheterized bladders in vivo or bladder transitional-like epithelial cells in vitro. Thus, the bladder habitat has barrier(s) to R state-mediated colonization possibly conferred by the terminally differentiated bladder epithelium and/or decoy receptors in urine. Together, our studies reveal the conformational landscape in solution, binding mechanisms, and adhesive strength of an allosteric two-domain adhesin that evolved "moderate" affinity to optimize persistence in the bladder during UTI.
Collapse
Affiliation(s)
- Vasilios Kalas
- Center for Women’s Infectious Disease Research, Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Jerome S. Pinkner
- Center for Women’s Infectious Disease Research, Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Thomas J. Hannan
- Center for Women’s Infectious Disease Research, Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Michael E. Hibbing
- Center for Women’s Infectious Disease Research, Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Karen W. Dodson
- Center for Women’s Infectious Disease Research, Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Alex S. Holehouse
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
- Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Hao Zhang
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Niraj H. Tolia
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Michael L. Gross
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Rohit V. Pappu
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
- Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - James Janetka
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Scott J. Hultgren
- Center for Women’s Infectious Disease Research, Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
- Corresponding author.
| |
Collapse
|
55
|
Abstract
Urinary tract infections (UTI) are among the most common bacterial infections in humans, affecting millions of people every year. UTI cause significant morbidity in women throughout their lifespan, in infant boys, in older men, in individuals with underlying urinary tract abnormalities, and in those that require long-term urethral catheterization, such as patients with spinal cord injuries or incapacitated individuals living in nursing homes. Serious sequelae include frequent recurrences, pyelonephritis with sepsis, renal damage in young children, pre-term birth, and complications of frequent antimicrobial use including high-level antibiotic resistance and Clostridium difficile colitis. Uropathogenic E. coli (UPEC) cause the vast majority of UTI, but less common pathogens such as Enterococcus faecalis and other enterococci frequently take advantage of an abnormal or catheterized urinary tract to cause opportunistic infections. While antibiotic therapy has historically been very successful in controlling UTI, the high rate of recurrence remains a major problem, and many individuals suffer from chronically recurring UTI, requiring long-term prophylactic antibiotic regimens to prevent recurrent UTI. Furthermore, the global emergence of multi-drug resistant UPEC in the past ten years spotlights the need for alternative therapeutic and preventative strategies to combat UTI, including anti-infective drug therapies and vaccines. In this chapter, we review recent advances in the field of UTI pathogenesis, with an emphasis on the identification of promising drug and vaccine targets. We then discuss the development of new UTI drugs and vaccines, highlighting the challenges these approaches face and the need for a greater understanding of urinary tract mucosal immunity.
Collapse
|
56
|
Sarowar S, Hu OJ, Werneburg GT, Thanassi DG, Li H. The Escherichia coli P and Type 1 Pilus Assembly Chaperones PapD and FimC Are Monomeric in Solution. J Bacteriol 2016; 198:2360-9. [PMID: 27353649 PMCID: PMC4984555 DOI: 10.1128/jb.00366-16] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 06/19/2016] [Indexed: 01/07/2023] Open
Abstract
UNLABELLED The chaperone/usher pathway is used by Gram-negative bacteria to assemble adhesive surface structures known as pili or fimbriae. Uropathogenic strains of Escherichia coli use this pathway to assemble P and type 1 pili, which facilitate colonization of the kidney and bladder, respectively. Pilus assembly requires a periplasmic chaperone and outer membrane protein termed the usher. The chaperone allows folding of pilus subunits and escorts the subunits to the usher for polymerization into pili and secretion to the cell surface. Based on previous structures of mutant versions of the P pilus chaperone PapD, it was suggested that the chaperone dimerizes in the periplasm as a self-capping mechanism. Such dimerization is counterintuitive because the chaperone G1 strand, important for chaperone-subunit interaction, is buried at the dimer interface. Here, we show that the wild-type PapD chaperone also forms a dimer in the crystal lattice; however, the dimer interface is different from the previously solved structures. In contrast to the crystal structures, we found that both PapD and the type 1 pilus chaperone, FimC, are monomeric in solution. Our findings indicate that pilus chaperones do not sequester their G1 β-strand by forming a dimer. Instead, the chaperones may expose their G1 strand for facile interaction with pilus subunits. We also found that the type 1 pilus adhesin, FimH, is flexible in solution while in complex with its chaperone, whereas the P pilus adhesin, PapGII, is rigid. Our study clarifies a crucial step in pilus biogenesis and reveals pilus-specific differences that may relate to biological function. IMPORTANCE Pili are critical virulence factors for many bacterial pathogens. Uropathogenic E. coli relies on P and type 1 pili assembled by the chaperone/usher pathway to adhere to the urinary tract and establish infection. Studying pilus assembly is important for understanding mechanisms of protein secretion, as well as for identifying points for therapeutic intervention. Pilus biogenesis is a multistep process. This work investigates the oligomeric state of the pilus chaperone in the periplasm, which is important for understanding early assembly events. Our work unambiguously demonstrates that both PapD and FimC chaperones are monomeric in solution. We further demonstrate that the solution behavior of the FimH and PapGII adhesins differ, which may be related to functional differences between the two pilus systems.
Collapse
Affiliation(s)
- Samema Sarowar
- Department of Biochemistry and Cell Biology, Stony Brook University, Stonybrook, New York, USA Biology Department, Brookhaven National Laboratory, Stonybrook, New York, USA
| | - Olivia J Hu
- Department of Biochemistry and Cell Biology, Stony Brook University, Stonybrook, New York, USA Biology Department, Brookhaven National Laboratory, Stonybrook, New York, USA
| | - Glenn T Werneburg
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stonybrook, New York, USA Center for Infectious Diseases, Stony Brook University, Stonybrook, New York, USA
| | - David G Thanassi
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stonybrook, New York, USA Center for Infectious Diseases, Stony Brook University, Stonybrook, New York, USA
| | - Huilin Li
- Department of Biochemistry and Cell Biology, Stony Brook University, Stonybrook, New York, USA Biology Department, Brookhaven National Laboratory, Stonybrook, New York, USA
| |
Collapse
|
57
|
Noinaj N, Mayclin S, Stanley AM, Jao CC, Buchanan SK. From Constructs to Crystals - Towards Structure Determination of β-barrel Outer Membrane Proteins. J Vis Exp 2016. [PMID: 27404000 DOI: 10.3791/53245] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Membrane proteins serve important functions in cells such as nutrient transport, motility, signaling, survival and virulence, yet constitute only ~1% percent of known structures. There are two types of membrane proteins, α-helical and β-barrel. While α-helical membrane proteins can be found in nearly all cellular membranes, β-barrel membrane proteins can only be found in the outer membranes of mitochondria, chloroplasts, and Gram-negative bacteria. One common bottleneck in structural studies of membrane proteins in general is getting enough pure sample for analysis. In hopes of assisting those interested in solving the structure of their favorite β-barrel outer membrane protein (OMP), general protocols are presented for the production of target β-barrel OMPs at levels useful for structure determination by either X-ray crystallography and/or NMR spectroscopy. Here, we outline construct design for both native expression and for expression into inclusion bodies, purification using an affinity tag, and crystallization using detergent screening, bicelle, and lipidic cubic phase techniques. These protocols have been tested and found to work for most OMPs from Gram-negative bacteria; however, there are some targets, particularly for mitochondria and chloroplasts that may require other methods for expression and purification. As such, the methods here should be applicable for most projects that involve OMPs from Gram-negative bacteria, yet the expression levels and amount of purified sample will vary depending on the target OMP.
Collapse
Affiliation(s)
- Nicholas Noinaj
- Department of Biological Sciences, Markey Center for Structural Biology, Purdue University;
| | - Stephen Mayclin
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health
| | - Ann M Stanley
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health; National Institute of General Medical Sciences (NIGMS), National Institutes of Health
| | - Christine C Jao
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health; National Institute of General Medical Sciences (NIGMS), National Institutes of Health
| | - Susan K Buchanan
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health
| |
Collapse
|
58
|
Pham T, Werneburg GT, Henderson NS, Thanassi DG, Delcour AH. Effect of chaperone-adhesin complex on plug release by the PapC usher. FEBS Lett 2016; 590:2172-9. [PMID: 27313078 DOI: 10.1002/1873-3468.12257] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Revised: 06/13/2016] [Accepted: 06/14/2016] [Indexed: 11/06/2022]
Abstract
The P pilus of uropathogenic Escherichia coli is a multisubunit fiber assembled at the outer membrane in a defined sequence by a chaperone/usher secretion system, comprising a periplasmic chaperone and a beta-barrel outer membrane protein, the PapC usher. To gain insight into the pilus biogenesis mechanism, we used patch clamp electrophysiology to investigate the effect of the initiating adhesin subunit, as it is delivered to PapC in a complex with the chaperone. We show that the chaperone-adhesin complex facilitates opening of the PapC pore and appears to engage within the PapC lumen, in agreement with prior biochemical and structural data.
Collapse
Affiliation(s)
- Thieng Pham
- Department of Biology and Biochemistry, University of Houston, TX, USA
| | - Glenn T Werneburg
- Department of Molecular Genetics and Microbiology, Center for Infectious Diseases, Stony Brook University, NY, USA
| | - Nadine S Henderson
- Department of Molecular Genetics and Microbiology, Center for Infectious Diseases, Stony Brook University, NY, USA
| | - David G Thanassi
- Department of Molecular Genetics and Microbiology, Center for Infectious Diseases, Stony Brook University, NY, USA
| | - Anne H Delcour
- Department of Biology and Biochemistry, University of Houston, TX, USA
| |
Collapse
|
59
|
Stubenrauch C, Belousoff MJ, Hay ID, Shen HH, Lillington J, Tuck KL, Peters KM, Phan MD, Lo AW, Schembri MA, Strugnell RA, Waksman G, Lithgow T. Effective assembly of fimbriae in Escherichia coli depends on the translocation assembly module nanomachine. Nat Microbiol 2016; 1:16064. [DOI: 10.1038/nmicrobiol.2016.64] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 04/07/2016] [Indexed: 01/08/2023]
|
60
|
Pham T, Henderson NS, Werneburg GT, Thanassi DG, Delcour AH. Electrostatic networks control plug stabilization in the PapC usher. Mol Membr Biol 2016; 32:198-207. [PMID: 27181766 DOI: 10.3109/09687688.2016.1160450] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The PapC usher, a β-barrel pore in the outer membrane of uropathogenic Escherichia coli, is used for assembly of the P pilus, a key virulence factor in bacterial colonization of human kidney cells. Each PapC protein is composed of a 24-stranded β-barrel channel, flanked by N- and C-terminal globular domains protruding into the periplasm, and occluded by a plug domain (PD). The PD is displaced from the channel towards the periplasm during pilus biogenesis, but the molecular mechanism for PD displacement remains unclear. Two structural features within the β-barrel, an α-helix and β5-6 hairpin loop, may play roles in controlling plug stabilization. Here we have tested clusters of residues at the interface of the plug, barrel, α-helix and hairpin, which participate in electrostatic networks. To assess the roles of these residues in plug stabilization, we used patch-clamp electrophysiology to compare the activity of wild-type and mutant PapC channels containing alanine substitutions at these sites. Mutations interrupting each of two salt bridge networks were relatively ineffective in disrupting plug stabilization. However, mutation of two pairs of arginines located at the inner and the outer surfaces of the PD resulted in an enhanced propensity for plug displacement. One arginine pair involved in a repulsive interaction between the linkers that tether the plug to the β-barrel was particularly sensitive to mutation. These results suggest that plug displacement, which is necessary for pilus assembly and translocation, may require a weakening of key electrostatic interactions between the plug linkers, and the plug and the α-helix.
Collapse
Affiliation(s)
- Thieng Pham
- a Department of Biology and Biochemistry , University of Houston , Houston , TX and
| | - Nadine S Henderson
- b Center for Infectious Diseases and Department of Molecular Genetics and Microbiology, Stony Brook University , Stony Brook , NY , USA
| | - Glenn T Werneburg
- b Center for Infectious Diseases and Department of Molecular Genetics and Microbiology, Stony Brook University , Stony Brook , NY , USA
| | - David G Thanassi
- b Center for Infectious Diseases and Department of Molecular Genetics and Microbiology, Stony Brook University , Stony Brook , NY , USA
| | - Anne H Delcour
- a Department of Biology and Biochemistry , University of Houston , Houston , TX and
| |
Collapse
|
61
|
Nitazoxanide Inhibits Pilus Biogenesis by Interfering with Folding of the Usher Protein in the Outer Membrane. Antimicrob Agents Chemother 2016; 60:2028-38. [PMID: 26824945 DOI: 10.1128/aac.02221-15] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Accepted: 01/07/2016] [Indexed: 12/21/2022] Open
Abstract
Many bacterial pathogens assemble surface fibers termed pili or fimbriae that facilitate attachment to host cells and colonization of host tissues. The chaperone/usher (CU) pathway is a conserved secretion system that is responsible for the assembly of virulence-associated pili by many different Gram-negative bacteria. Pilus biogenesis by the CU pathway requires a dedicated periplasmic chaperone and an integral outer membrane (OM) assembly and secretion platform termed the usher. Nitazoxanide (NTZ), an antiparasitic drug, was previously shown to inhibit the function of aggregative adherence fimbriae and type 1 pili assembled by the CU pathway in enteroaggregativeEscherichia coli, an important causative agent of diarrhea. We show here that NTZ also inhibits the function of type 1 and P pili from uropathogenicE. coli(UPEC). UPEC is the primary causative agent of urinary tract infections, and type 1 and P pili mediate colonization of the bladder and kidneys, respectively. By analysis of the different stages of the CU pilus biogenesis pathway, we show that treatment of bacteria with NTZ causes a reduction in the number of usher molecules in the OM, resulting in a loss of pilus assembly on the bacterial surface. In addition, we determine that NTZ specifically prevents proper folding of the usher β-barrel domain in the OM. Our findings demonstrate that NTZ is a pilicide with a novel mechanism of action and activity against diverse CU pathways. This suggests that further development of the NTZ scaffold may lead to new antivirulence agents that target the usher to prevent pilus assembly.
Collapse
|
62
|
Spaulding CN, Hultgren SJ. Adhesive Pili in UTI Pathogenesis and Drug Development. Pathogens 2016; 5:E30. [PMID: 26999218 PMCID: PMC4810151 DOI: 10.3390/pathogens5010030] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 02/15/2016] [Accepted: 03/07/2016] [Indexed: 01/08/2023] Open
Abstract
Urinary tract infections (UTIs) are one of the most common bacterial infections, affecting 150 million people each year worldwide. High recurrence rates and increasing antimicrobial resistance among uropathogens are making it imperative to develop alternative strategies for the treatment and prevention of this common infection. In this Review, we discuss how understanding the: (i) molecular and biophysical basis of host-pathogen interactions; (ii) consequences of the molecular cross-talk at the host pathogen interface in terms of disease progression; and (iii) pathophysiology of UTIs is leading to efforts to translate this knowledge into novel therapeutics to treat and prevent these infections.
Collapse
Affiliation(s)
- Caitlin N Spaulding
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
| | - Scott J Hultgren
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
- Center for Women's Infectious Disease Research, Washington University School of Medicine, St. Louis, MO 63110, USA.
| |
Collapse
|
63
|
Hospenthal MK, Redzej A, Dodson K, Ukleja M, Frenz B, Rodrigues C, Hultgren SJ, DiMaio F, Egelman EH, Waksman G. Structure of a Chaperone-Usher Pilus Reveals the Molecular Basis of Rod Uncoiling. Cell 2016; 164:269-278. [PMID: 26724865 PMCID: PMC4715182 DOI: 10.1016/j.cell.2015.11.049] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 11/01/2015] [Accepted: 11/16/2015] [Indexed: 11/24/2022]
Abstract
Types 1 and P pili are prototypical bacterial cell-surface appendages playing essential roles in mediating adhesion of bacteria to the urinary tract. These pili, assembled by the chaperone-usher pathway, are polymers of pilus subunits assembling into two parts: a thin, short tip fibrillum at the top, mounted on a long pilus rod. The rod adopts a helical quaternary structure and is thought to play essential roles: its formation may drive pilus extrusion by preventing backsliding of the nascent growing pilus within the secretion pore; the rod also has striking spring-like properties, being able to uncoil and recoil depending on the intensity of shear forces generated by urine flow. Here, we present an atomic model of the P pilus generated from a 3.8 Å resolution cryo-electron microscopy reconstruction. This structure provides the molecular basis for the rod's remarkable mechanical properties and illuminates its role in pilus secretion.
Collapse
Affiliation(s)
- Manuela K Hospenthal
- Institute of Structural and Molecular Biology, University College London and Birkbeck, Malet Street, London, WC1E 7HX, UK
| | - Adam Redzej
- Institute of Structural and Molecular Biology, University College London and Birkbeck, Malet Street, London, WC1E 7HX, UK
| | - Karen Dodson
- Center for Women's Infectious Disease Research and Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63011, USA
| | - Marta Ukleja
- Institute of Structural and Molecular Biology, University College London and Birkbeck, Malet Street, London, WC1E 7HX, UK
| | - Brandon Frenz
- Department of Biochemistry, University of Washington, Seattle, WA 98105, USA
| | - Catarina Rodrigues
- Institute of Structural and Molecular Biology, University College London and Birkbeck, Malet Street, London, WC1E 7HX, UK
| | - Scott J Hultgren
- Center for Women's Infectious Disease Research and Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63011, USA
| | - Frank DiMaio
- Department of Biochemistry, University of Washington, Seattle, WA 98105, USA
| | - Edward H Egelman
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22901, USA.
| | - Gabriel Waksman
- Institute of Structural and Molecular Biology, University College London and Birkbeck, Malet Street, London, WC1E 7HX, UK.
| |
Collapse
|
64
|
Abstract
Type IV secretion systems (T4SSs) are large multisubunit translocons, found in both gram-negative and gram-positive bacteria and in some archaea. These systems transport a diverse array of substrates from DNA and protein-DNA complexes to proteins, and play fundamental roles in both bacterial pathogenesis and bacterial adaptation to the cellular milieu in which bacteria live. This review describes the various biochemical and structural advances made toward understanding the biogenesis, architecture, and function of T4SSs.
Collapse
Affiliation(s)
- Vidya Chandran Darbari
- Section of Structural Biology, Department of Medicine, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | | |
Collapse
|
65
|
Pakharukova N, Garnett JA, Tuittila M, Paavilainen S, Diallo M, Xu Y, Matthews SJ, Zavialov AV. Structural Insight into Archaic and Alternative Chaperone-Usher Pathways Reveals a Novel Mechanism of Pilus Biogenesis. PLoS Pathog 2015; 11:e1005269. [PMID: 26587649 PMCID: PMC4654587 DOI: 10.1371/journal.ppat.1005269] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 10/22/2015] [Indexed: 11/18/2022] Open
Abstract
Gram-negative pathogens express fibrous adhesive organelles that mediate targeting to sites of infection. The major class of these organelles is assembled via the classical, alternative and archaic chaperone-usher pathways. Although non-classical systems share a wider phylogenetic distribution and are associated with a range of diseases, little is known about their assembly mechanisms. Here we report atomic-resolution insight into the structure and biogenesis of Acinetobacter baumannii Csu and Escherichia coli ECP biofilm-mediating pili. We show that the two non-classical systems are structurally related, but their assembly mechanism is strikingly different from the classical assembly pathway. Non-classical chaperones, unlike their classical counterparts, maintain subunits in a substantially disordered conformational state, akin to a molten globule. This is achieved by a unique binding mechanism involving the register-shifted donor strand complementation and a different subunit carboxylate anchor. The subunit lacks the classical pre-folded initiation site for donor strand exchange, suggesting that recognition of its exposed hydrophobic core starts the assembly process and provides fresh inspiration for the design of inhibitors targeting chaperone-usher systems.
Collapse
Affiliation(s)
- Natalia Pakharukova
- Department of Chemistry, University of Turku, Turku, JBL, Arcanum, Turku, Finland
| | - James A. Garnett
- Centre for Structural Biology, Department of Life Sciences, Imperial College London, South Kensington, London, United Kingdom
| | - Minna Tuittila
- Department of Chemistry, University of Turku, Turku, JBL, Arcanum, Turku, Finland
| | - Sari Paavilainen
- Department of Chemistry, University of Turku, Turku, JBL, Arcanum, Turku, Finland
| | - Mamou Diallo
- Centre for Structural Biology, Department of Life Sciences, Imperial College London, South Kensington, London, United Kingdom
| | - Yingqi Xu
- Centre for Structural Biology, Department of Life Sciences, Imperial College London, South Kensington, London, United Kingdom
| | - Steve J. Matthews
- Centre for Structural Biology, Department of Life Sciences, Imperial College London, South Kensington, London, United Kingdom
| | - Anton V. Zavialov
- Department of Chemistry, University of Turku, Turku, JBL, Arcanum, Turku, Finland
- * E-mail:
| |
Collapse
|
66
|
Wurpel DJ, Totsika M, Allsopp LP, Webb RI, Moriel DG, Schembri MA. Comparative proteomics of uropathogenic Escherichia coli during growth in human urine identify UCA-like (UCL) fimbriae as an adherence factor involved in biofilm formation and binding to uroepithelial cells. J Proteomics 2015; 131:177-189. [PMID: 26546558 DOI: 10.1016/j.jprot.2015.11.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Revised: 10/23/2015] [Accepted: 11/02/2015] [Indexed: 01/15/2023]
Abstract
Uropathogenic Escherichia coli (UPEC) are the primary cause of urinary tract infection (UTI) in humans. For the successful colonisation of the human urinary tract, UPEC employ a diverse collection of secreted or surface-exposed virulence factors including toxins, iron acquisition systems and adhesins. In this study, a comparative proteomic approach was utilised to define the UPEC pan and core surface proteome following growth in pooled human urine. Identified proteins were investigated for subcellular origin, prevalence and homology to characterised virulence factors. Fourteen core surface proteins were identified, as well as eleven iron uptake receptor proteins and four distinct fimbrial types, including type 1, P, F1C/S and a previously uncharacterised fimbrial type, designated UCA-like (UCL) fimbriae in this study. These pathogenicity island (PAI)-associated fimbriae are related to UCA fimbriae of Proteus mirabilis, associated with UPEC and exclusively found in members of the E. coli B2 and D phylogroup. We further demonstrated that UCL fimbriae promote significant biofilm formation on abiotic surfaces and mediate specific attachment to exfoliated human uroepithelial cells. Combined, this study has defined the surface proteomic profiles and core surface proteome of UPEC during growth in human urine and identified a new type of fimbriae that may contribute to UTI.
Collapse
Affiliation(s)
- Daniël J Wurpel
- Australian Infectious Disease Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia
| | - Makrina Totsika
- Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology, Brisbane, Australia
| | - Luke P Allsopp
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Richard I Webb
- Centre for Microscopy and Microanalysis, The University of Queensland, Brisbane, Australia
| | - Danilo G Moriel
- Australian Infectious Disease Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia
| | - Mark A Schembri
- Australian Infectious Disease Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia.
| |
Collapse
|
67
|
Van Gerven N, Klein RD, Hultgren SJ, Remaut H. Bacterial amyloid formation: structural insights into curli biogensis. Trends Microbiol 2015; 23:693-706. [PMID: 26439293 DOI: 10.1016/j.tim.2015.07.010] [Citation(s) in RCA: 118] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Revised: 07/06/2015] [Accepted: 07/22/2015] [Indexed: 01/20/2023]
Abstract
Curli are functional amyloid fibers assembled by many Gram-negative bacteria as part of an extracellular matrix that encapsulates the bacteria within a biofilm. A multicomponent secretion system ensures the safe transport of the aggregation-prone curli subunits across the periplasm and outer membrane, and coordinates subunit self-assembly into surface-attached fibers. To avoid the build-up of potentially toxic intracellular protein aggregates, the timing and location of the interactions of the different curli proteins are of paramount importance. Here we review the structural and molecular biology of curli biogenesis, with a focus on the recent breakthroughs in our understanding of subunit chaperoning and secretion. The mechanistic insight into the curli assembly pathway will provide tools for new biotechnological applications and inform the design of targeted inhibitors of amyloid polymerization and biofilm formation.
Collapse
Affiliation(s)
- Nani Van Gerven
- Structural and Molecular Microbiology, Structural Biology Research Center, VIB, Pleinlaan 2, 1050 Brussels, Belgium; Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
| | - Roger D Klein
- Department of Molecular Microbiology and Microbial Pathogenesis, Washington University in Saint Louis School of Medicine, St Louis, MO 63110-1010, USA
| | - Scott J Hultgren
- Department of Molecular Microbiology and Microbial Pathogenesis, Washington University in Saint Louis School of Medicine, St Louis, MO 63110-1010, USA
| | - Han Remaut
- Structural and Molecular Microbiology, Structural Biology Research Center, VIB, Pleinlaan 2, 1050 Brussels, Belgium; Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium.
| |
Collapse
|
68
|
Chahales P, Thanassi DG. Structure, Function, and Assembly of Adhesive Organelles by Uropathogenic Bacteria. Microbiol Spectr 2015; 3:10.1128/microbiolspec.UTI-0018-2013. [PMID: 26542038 PMCID: PMC4638162 DOI: 10.1128/microbiolspec.uti-0018-2013] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Indexed: 01/02/2023] Open
Abstract
Bacteria assemble a wide range of adhesive proteins, termed adhesins, to mediate binding to receptors and colonization of surfaces. For pathogenic bacteria, adhesins are critical for early stages of infection, allowing the bacteria to initiate contact with host cells, colonize different tissues, and establish a foothold within the host. The adhesins expressed by a pathogen are also critical for bacterial-bacterial interactions and the formation of bacterial communities, including biofilms. The ability to adhere to host tissues is particularly important for bacteria that colonize sites such as the urinary tract, where the flow of urine functions to maintain sterility by washing away non-adherent pathogens. Adhesins vary from monomeric proteins that are directly anchored to the bacterial surface to polymeric, hair-like fibers that extend out from the cell surface. These latter fibers are termed pili or fimbriae, and were among the first identified virulence factors of uropathogenic Escherichia coli. Studies since then have identified a range of both pilus and non-pilus adhesins that contribute to bacterial colonization of the urinary tract, and have revealed molecular details of the structures, assembly pathways, and functions of these adhesive organelles. In this review, we describe the different types of adhesins expressed by both Gram-negative and Gram-positive uropathogens, what is known about their structures, how they are assembled on the bacterial surface, and the functions of specific adhesins in the pathogenesis of urinary tract infections.
Collapse
Affiliation(s)
- Peter Chahales
- Center for Infectious Diseases and Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794
| | - David G Thanassi
- Center for Infectious Diseases and Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794
| |
Collapse
|
69
|
The pilus usher controls protein interactions via domain masking and is functional as an oligomer. Nat Struct Mol Biol 2015; 22:540-6. [PMID: 26052892 PMCID: PMC4496297 DOI: 10.1038/nsmb.3044] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Accepted: 05/12/2015] [Indexed: 12/21/2022]
Abstract
The chaperone-usher (CU) pathway assembles organelles termed pili or
fimbriae in Gram-negative bacteria. Type 1 pili expressed by uropathogenic
Escherichia coli are prototypical structures assembled by
the CU pathway. Biogenesis of pili by the CU pathway requires a periplasmic
chaperone and an outer membrane protein termed the usher (FimD). We show that
the FimD C-terminal domains provide the high-affinity substrate binding site,
but that these domains are masked in the resting usher. Domain masking requires
the FimD plug domain, which serves as a switch controlling usher activation. We
demonstrate that usher molecules can act in trans for pilus
biogenesis, providing conclusive evidence for a functional usher oligomer. These
results reveal mechanisms by which molecular machines such as the usher regulate
and harness protein-protein interactions, and suggest that ushers may interact
in a cooperative manner during pilus assembly in bacteria.
Collapse
|
70
|
Pakharukova N, Tuittila M, Paavilainen S, Zavialov A. Crystallization and preliminary X-ray diffraction analysis of the Csu pili CsuC-CsuA/B chaperone-major subunit pre-assembly complex from Acinetobacter baumannii. Acta Crystallogr F Struct Biol Commun 2015; 71:770-4. [PMID: 26057810 PMCID: PMC4461345 DOI: 10.1107/s2053230x15007955] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 04/21/2015] [Indexed: 11/10/2022] Open
Abstract
The attachment of many Gram-negative pathogens to biotic and abiotic surfaces is mediated by fimbrial adhesins, which are assembled via the classical, alternative and archaic chaperone-usher (CU) pathways. The archaic CU fimbrial adhesins have the widest phylogenetic distribution, yet very little is known about their structure and mechanism of assembly. To elucidate the biogenesis of archaic CU systems, structural analysis of the Csu fimbriae, which are used by Acinetobacter baumannii to form stable biofilms and cause nosocomial infection, was focused on. The major fimbriae subunit CsuA/B complexed with the CsuC chaperone was purified from the periplasm of Escherichia coli cells co-expressing CsuA/B and CsuC, and the complex was crystallized in PEG 3350 solution using the hanging-drop vapour-diffusion method. Selenomethionine-labelled CsuC-CsuA/B complex was purified and crystallized under the same conditions. The crystals diffracted to 2.40 Å resolution and belonged to the hexagonal space group P6(4)22, with unit-cell parameters a = b = 94.71, c = 187.05 Å, α = β = 90, γ = 120°. Initial phases were derived from a single anomalous diffraction (SAD) experiment using the selenomethionine derivative.
Collapse
Affiliation(s)
- Natalia Pakharukova
- Department of Chemistry, University of Turku, Joint Biotechnology Laboratory, Arcanum, Vatselankatu 2, 20500 Turku, Finland
| | - Minna Tuittila
- Department of Chemistry, University of Turku, Joint Biotechnology Laboratory, Arcanum, Vatselankatu 2, 20500 Turku, Finland
| | - Sari Paavilainen
- Department of Chemistry, University of Turku, Joint Biotechnology Laboratory, Arcanum, Vatselankatu 2, 20500 Turku, Finland
| | - Anton Zavialov
- Department of Chemistry, University of Turku, Joint Biotechnology Laboratory, Arcanum, Vatselankatu 2, 20500 Turku, Finland
| |
Collapse
|
71
|
Columbus L. Post-expression strategies for structural investigations of membrane proteins. Curr Opin Struct Biol 2015; 32:131-8. [PMID: 25951412 DOI: 10.1016/j.sbi.2015.04.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 04/14/2015] [Accepted: 04/14/2015] [Indexed: 01/26/2023]
Abstract
Currently, membrane proteins only comprise 1.5% of the protein data bank and, thus, still remain a challenge for structural biologists. Expression, stabilization in membrane mimics (e.g. detergent), heterogeneity (conformational and chemical), and crystallization in the presence of a membrane mimic are four major bottlenecks encountered. In response, several post-expression protein modifications have been utilized to facilitate structure determination of membrane proteins. This review highlights four approaches: limited proteolysis, deglycosylation, cysteine alkylation, and lysine methylation. Combined these approaches have facilitated the structure determination of more than 40 membrane proteins and, therefore, are a useful addition to the membrane protein structural biologist's toolkit.
Collapse
Affiliation(s)
- Linda Columbus
- Department of Chemistry, University of Virginia, Charlottesville, VA 22902, United States.
| |
Collapse
|
72
|
Costa TRD, Felisberto-Rodrigues C, Meir A, Prevost MS, Redzej A, Trokter M, Waksman G. Secretion systems in Gram-negative bacteria: structural and mechanistic insights. Nat Rev Microbiol 2015; 13:343-59. [DOI: 10.1038/nrmicro3456] [Citation(s) in RCA: 655] [Impact Index Per Article: 72.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
|
73
|
Kleinschmidt JH. Folding of β-barrel membrane proteins in lipid bilayers - Unassisted and assisted folding and insertion. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:1927-43. [PMID: 25983306 DOI: 10.1016/j.bbamem.2015.05.004] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2015] [Revised: 05/06/2015] [Accepted: 05/07/2015] [Indexed: 01/08/2023]
Abstract
In cells, β-barrel membrane proteins are transported in unfolded form to an outer membrane into which they fold and insert. Model systems have been established to investigate the mechanisms of insertion and folding of these versatile proteins into detergent micelles, lipid bilayers and even synthetic amphipathic polymers. In these experiments, insertion into lipid membranes is initiated from unfolded forms that do not display residual β-sheet secondary structure. These studies therefore have allowed the investigation of membrane protein folding and insertion in great detail. Folding of β-barrel membrane proteins into lipid bilayers has been monitored from unfolded forms by dilution of chaotropic denaturants that keep the protein unfolded as well as from unfolded forms present in complexes with molecular chaperones from cells. This review is aimed to provide an overview of the principles and mechanisms observed for the folding of β-barrel transmembrane proteins into lipid bilayers, the importance of lipid-protein interactions and the function of molecular chaperones and folding assistants. This article is part of a Special Issue entitled: Lipid-protein interactions.
Collapse
Affiliation(s)
- Jörg H Kleinschmidt
- Abteilung Biophysik, Institut für Biologie, FB 10, Universität Kassel and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), Heinrich-Plett-Str. 40, D-34132 Kassel, Germany.
| |
Collapse
|
74
|
Affiliation(s)
- Alain Filloux
- Alain Filloux, MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London SW7 2AZ, UK; E-mail:
| |
Collapse
|
75
|
Busch A, Phan G, Waksman G. Molecular mechanism of bacterial type 1 and P pili assembly. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2015; 373:rsta.2013.0153. [PMID: 25624519 DOI: 10.1098/rsta.2013.0153] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The formation of adhesive surface structures called pili or fimbriae ('bacterial hair') is an important contributor towards bacterial pathogenicity and persistence. To fight often chronic or recurrent bacterial infections such as urinary tract infections, it is necessary to understand the molecular mechanism of the nanomachines assembling such pili. Here, we focus on the so far best-known pilus assembly machinery: the chaperone-usher pathway producing the type 1 and P pili, and highlight the most recently acquired structural knowledge. First, we describe the subunits' structure and the molecular role of the periplasmic chaperone. Second, we focus on the outer-membrane usher structure and the catalytic mechanism of usher-mediated pilus biogenesis. Finally, we describe how the detailed understanding of the chaperone-usher pathway at a molecular level has paved the way for the design of a new generation of bacterial inhibitors called 'pilicides'.
Collapse
Affiliation(s)
- Andreas Busch
- Institute of Structural and Molecular Biology, University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK
| | - Gilles Phan
- Institute of Structural and Molecular Biology, University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK
| | - Gabriel Waksman
- Institute of Structural and Molecular Biology, University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK
| |
Collapse
|
76
|
Ruer S, Pinotsis N, Steadman D, Waksman G, Remaut H. Virulence-targeted Antibacterials: Concept, Promise, and Susceptibility to Resistance Mechanisms. Chem Biol Drug Des 2015; 86:379-99. [DOI: 10.1111/cbdd.12517] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 12/23/2014] [Accepted: 01/06/2015] [Indexed: 12/25/2022]
Affiliation(s)
- Ségolène Ruer
- Structural and Molecular Microbiology; Structural Biology Research Center; VIB; Pleinlaan 2 Brussels 1050 Belgium
- Structural Biology Brussels; Vrije Universiteit Brussel; Pleinlaan 2 Brussels 1050 Belgium
| | - Nikos Pinotsis
- Institute of Structural and Molecular Biology (ISMB); UCL and Birkbeck College; London WC1E 7HX UK
| | - David Steadman
- Wolfson Institute for Biomedical Research (WIBR); UCL; London WC1E 6BT UK
| | - Gabriel Waksman
- Institute of Structural and Molecular Biology (ISMB); UCL and Birkbeck College; London WC1E 7HX UK
| | - Han Remaut
- Structural and Molecular Microbiology; Structural Biology Research Center; VIB; Pleinlaan 2 Brussels 1050 Belgium
- Structural Biology Brussels; Vrije Universiteit Brussel; Pleinlaan 2 Brussels 1050 Belgium
| |
Collapse
|
77
|
Moonens K, Van den Broeck I, De Kerpel M, Deboeck F, Raymaekers H, Remaut H, De Greve H. Structural and functional insight into the carbohydrate receptor binding of F4 fimbriae-producing enterotoxigenic Escherichia coli. J Biol Chem 2015; 290:8409-19. [PMID: 25631050 DOI: 10.1074/jbc.m114.618595] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) strains are important causes of intestinal disease in humans and lead to severe production losses in animal farming. A range of fimbrial adhesins in ETEC strains determines host and tissue tropism. ETEC strains expressing F4 fimbriae are associated with neonatal and post-weaning diarrhea in piglets. Three naturally occurring variants of F4 fimbriae (F4ab, F4ac, and F4ad) exist that differ in the primary sequence of their major adhesive subunit FaeG, and each features a related yet distinct receptor binding profile. Here the x-ray structure of FaeGad bound to lactose provides the first structural insight into the receptor specificity and mode of binding by the poly-adhesive F4 fimbriae. A small D'-D″-α1-α2 subdomain grafted on the immunoglobulin-like core of FaeG hosts the carbohydrate binding site. Two short amino acid stretches Phe(150)-Glu(152) and Val(166)-Glu(170) of FaeGad bind the terminal galactose in the lactosyl unit and provide affinity and specificity to the interaction. A hemagglutination-based assay with E. coli expressing mutant F4ad fimbriae confirmed the elucidated co-complex structure. Interestingly, the crucial D'-α1 loop that borders the FaeGad binding site adopts a different conformation in the two other FaeG variants and hints at a heterogeneous binding pocket among the FaeG serotypes.
Collapse
Affiliation(s)
- Kristof Moonens
- From the Structural and Molecular Microbiology, VIB Structural Biology Research Center, 1050 Brussels, the Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, and
| | - Imke Van den Broeck
- From the Structural and Molecular Microbiology, VIB Structural Biology Research Center, 1050 Brussels, the Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, and
| | - Maia De Kerpel
- From the Structural and Molecular Microbiology, VIB Structural Biology Research Center, 1050 Brussels, the Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, and
| | - Francine Deboeck
- the Viral Genetics Laboratory, Vrije Universiteit Brussel, 1050 Brussels, Belgium
| | - Hanne Raymaekers
- From the Structural and Molecular Microbiology, VIB Structural Biology Research Center, 1050 Brussels, the Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, and
| | - Han Remaut
- From the Structural and Molecular Microbiology, VIB Structural Biology Research Center, 1050 Brussels, the Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, and
| | - Henri De Greve
- From the Structural and Molecular Microbiology, VIB Structural Biology Research Center, 1050 Brussels, the Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, and
| |
Collapse
|
78
|
Fatal attraction: how bacterial adhesins affect host signaling and what we can learn from them. Int J Mol Sci 2015; 16:2626-40. [PMID: 25625516 PMCID: PMC4346855 DOI: 10.3390/ijms16022626] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Revised: 12/25/2014] [Accepted: 01/19/2015] [Indexed: 12/20/2022] Open
Abstract
The ability of bacterial species to colonize and infect host organisms is critically dependent upon their capacity to adhere to cellular surfaces of the host. Adherence to cell surfaces is known to be essential for the activation and delivery of certain virulence factors, but can also directly affect host cell signaling to aid bacterial spread and survival. In this review we will discuss the recent advances in the field of bacterial adhesion, how we are beginning to unravel the effects adhesins have on host cell signaling, and how these changes aid the bacteria in terms of their survival and evasion of immune responses. Finally, we will highlight how the exploitation of bacterial adhesins may provide new therapeutic avenues for the treatment of a wide range of bacterial infections.
Collapse
|
79
|
Schwartz DJ, Conover MS, Hannan TJ, Hultgren SJ. Uropathogenic Escherichia coli superinfection enhances the severity of mouse bladder infection. PLoS Pathog 2015; 11:e1004599. [PMID: 25569799 PMCID: PMC4287616 DOI: 10.1371/journal.ppat.1004599] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2014] [Accepted: 12/02/2014] [Indexed: 01/07/2023] Open
Abstract
Urinary tract infections (UTIs) afflict over 9 million women in America every year, often necessitating long-term prophylactic antibiotics. One risk factor for UTI is frequent sexual intercourse, which dramatically increases the risk of UTI. The mechanism behind this increased risk is unknown; however, bacteriuria increases immediately after sexual intercourse episodes, suggesting that physical manipulation introduces periurethral flora into the urinary tract. In this paper, we investigated whether superinfection (repeat introduction of bacteria) resulted in increased risk of severe UTI, manifesting as persistent bacteriuria, high titer bladder bacterial burdens and chronic inflammation, an outcome referred to as chronic cystitis. Chronic cystitis represents unchecked luminal bacterial replication and is defined histologically by urothelial hyperplasia and submucosal lymphoid aggregates, a histological pattern similar to that seen in humans suffering chronic UTI. C57BL/6J mice are resistant to chronic cystitis after a single infection; however, they developed persistent bacteriuria and chronic cystitis when superinfected 24 hours apart. Elevated levels of interleukin-6 (IL-6), keratinocyte cytokine (KC/CXCL1), and granulocyte colony-stimulating factor (G-CSF) in the serum of C57BL/6J mice prior to the second infection predicted the development of chronic cystitis. These same cytokines have been found to precede chronic cystitis in singly infected C3H/HeN mice. Furthermore, inoculating C3H/HeN mice twice within a six-hour period doubled the proportion of mice that developed chronic cystitis. Intracellular bacterial replication, regulated hemolysin (HlyA) expression, and caspase 1/11 activation were essential for this increase. Microarrays conducted at four weeks post inoculation in both mouse strains revealed upregulation of IL-1 and antimicrobial peptides during chronic cystitis. These data suggest a mechanism by which caspase-1/11 activation and IL-1 secretion could predispose certain women to recurrent UTI after frequent intercourse, a predisposition predictable by several serum biomarkers in two murine models. Urinary tract infections (UTIs) affect millions of women each year resulting in substantial morbidity and lost wages. Approximately 1.5 million women are referred to urology clinics suffering from chronic recurrent UTI on a yearly basis necessitating the use of prophylactic antibiotics. Frequent and recent sexual intercourse correlates with the development of UTI, a phenomenon referred to clinically as “honeymoon cystitis.” Here, using superinfection mouse models, we identified bacterial and host factors that influence the likelihood of developing chronic UTI. We discovered that superinfection leads to a higher rate of chronic UTI, which depended on bacterial replication within bladder cells combined with an immune response including inflammasome activation and cytokine release. These data suggest that bacterial inoculation into an acutely inflamed urinary tract is more likely to lead to severe UTI than bacterial presence in the absence of inflammation. Modification of these risk factors could lead to new therapeutics that prevent the development of recurrent UTI.
Collapse
Affiliation(s)
- Drew J. Schwartz
- Department of Molecular Microbiology, Center for Women's Infectious Disease Research, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Matt S. Conover
- Department of Molecular Microbiology, Center for Women's Infectious Disease Research, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Thomas J. Hannan
- Department of Pathology & Immunology, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Scott J. Hultgren
- Department of Molecular Microbiology, Center for Women's Infectious Disease Research, Washington University in St. Louis, St. Louis, Missouri, United States of America
- * E-mail:
| |
Collapse
|
80
|
Moonens K, De Kerpel M, Coddens A, Cox E, Pardon E, Remaut H, De Greve H. Nanobody mediated inhibition of attachment of F18 Fimbriae expressing Escherichia coli. PLoS One 2014; 9:e114691. [PMID: 25502211 PMCID: PMC4263667 DOI: 10.1371/journal.pone.0114691] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2014] [Accepted: 11/12/2014] [Indexed: 11/19/2022] Open
Abstract
Post-weaning diarrhea and edema disease caused by F18 fimbriated E. coli are important diseases in newly weaned piglets and lead to severe production losses in farming industry. Protective treatments against these infections have thus far limited efficacy. In this study we generated nanobodies directed against the lectin domain of the F18 fimbrial adhesin FedF and showed in an in vitro adherence assay that four unique nanobodies inhibit the attachment of F18 fimbriated E. coli bacteria to piglet enterocytes. Crystallization of the FedF lectin domain with the most potent inhibitory nanobodies revealed their mechanism of action. These either competed with the binding of the blood group antigen receptor on the FedF surface or induced a conformational change in which the CDR3 region of the nanobody displaces the D″-E loop adjacent to the binding site. This D″-E loop was previously shown to be required for the interaction between F18 fimbriated bacteria and blood group antigen receptors in a membrane context. This work demonstrates the feasibility of inhibiting the attachment of fimbriated pathogens by employing nanobodies directed against the adhesin domain.
Collapse
Affiliation(s)
- Kristof Moonens
- Structural & Molecular Microbiology, Structural Biology Research Center, VIB, Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
| | - Maia De Kerpel
- Structural & Molecular Microbiology, Structural Biology Research Center, VIB, Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
| | - Annelies Coddens
- Department of Veterinary Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, Merelbeke 9820, Belgium
| | - Eric Cox
- Department of Veterinary Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, Merelbeke 9820, Belgium
| | - Els Pardon
- Structural & Molecular Microbiology, Structural Biology Research Center, VIB, Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
| | - Han Remaut
- Structural & Molecular Microbiology, Structural Biology Research Center, VIB, Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
| | - Henri De Greve
- Structural & Molecular Microbiology, Structural Biology Research Center, VIB, Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- * E-mail:
| |
Collapse
|
81
|
Salvadori E, Fung MW, Hoffmann M, Anderson HL, Kay CWM. Exploiting the Symmetry of the Resonator Mode to Enhance PELDOR Sensitivity. APPLIED MAGNETIC RESONANCE 2014; 46:359-368. [PMID: 25798030 PMCID: PMC4359710 DOI: 10.1007/s00723-014-0621-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Revised: 10/29/2014] [Indexed: 06/04/2023]
Abstract
Pulsed electron paramagnetic resonance (EPR) spectroscopy using microwaves at two frequencies can be employed to measure distances between pairs of paramagnets separated by up to 10 nm. The method, combined with site-directed mutagenesis, has become increasingly popular in structural biology for both its selectivity and capability of providing information not accessible through more standard methods such as nuclear magnetic resonance and X-ray crystallography. Despite these advantages, EPR distance measurements suffer from poor sensitivity. One contributing factor is technical: since 65 MHz typically separates the pump and detection frequencies, they cannot both be located at the center of the pseudo-Lorentzian microwave resonance of a single-mode resonator. To maximize the inversion efficiency, the pump pulse is usually placed at the center of the resonance, while the observer frequency is placed in the wing, with consequent reduction in sensitivity. Here, we consider an alternative configuration: by spacing pump and observer frequencies symmetrically with respect to the microwave resonance and by increasing the quality factor, valuable improvement in the signal-to-noise ratio can be obtained.
Collapse
Affiliation(s)
- Enrico Salvadori
- London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London, WC1H 0AH UK
- Institute of Structural and Molecular Biology, University College London, Gower Street, London, WC1E 6BT UK
| | - Mei Wai Fung
- Institute of Structural and Molecular Biology, University College London, Gower Street, London, WC1E 6BT UK
| | - Markus Hoffmann
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3TA UK
| | - Harry L. Anderson
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3TA UK
| | - Christopher W. M. Kay
- London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London, WC1H 0AH UK
- Institute of Structural and Molecular Biology, University College London, Gower Street, London, WC1E 6BT UK
| |
Collapse
|
82
|
Berry JL, Pelicic V. Exceptionally widespread nanomachines composed of type IV pilins: the prokaryotic Swiss Army knives. FEMS Microbiol Rev 2014; 39:134-54. [PMID: 25793961 PMCID: PMC4471445 DOI: 10.1093/femsre/fuu001] [Citation(s) in RCA: 178] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Prokaryotes have engineered sophisticated surface nanomachines that have allowed them to colonize Earth and thrive even in extreme environments. Filamentous machineries composed of type IV pilins, which are associated with an amazing array of properties ranging from motility to electric conductance, are arguably the most widespread since distinctive proteins dedicated to their biogenesis are found in most known species of prokaryotes. Several decades of investigations, starting with type IV pili and then a variety of related systems both in bacteria and archaea, have outlined common molecular and structural bases for these nanomachines. Using type IV pili as a paradigm, we will highlight in this review common aspects and key biological differences of this group of filamentous structures. Using type IV pili as a paradigm, we review common genetic, structural and mechanistic features (many) as well as differences (few) of the exceptionally widespread and functionally versatile prokaryotic nano-machines composed of type IV pilins.
Collapse
Affiliation(s)
- Jamie-Lee Berry
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London SW7 2AZ, UK
| | - Vladimir Pelicic
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London SW7 2AZ, UK
| |
Collapse
|
83
|
Abstract
A combination of computer simulations, evolutionary analysis and graph theory has provided new insights into the assembly of pili on the surface of bacteria.
Collapse
Affiliation(s)
- Han Remaut
- Han Remaut is in the VIB Structural Biology Research Center, Brussels, Belgium and is in the Structural Biology Brussels Lab, Vrije Universiteit Brussel, Brussels, Belgium
| | - Nir Ben-Tal
- Nir Ben-Tal is in the Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv, Israel
| |
Collapse
|
84
|
Farabella I, Pham T, Henderson NS, Geibel S, Phan G, Thanassi DG, Delcour AH, Waksman G, Topf M. Allosteric signalling in the outer membrane translocation domain of PapC usher. eLife 2014; 3:e03532. [PMID: 25271373 PMCID: PMC4356140 DOI: 10.7554/elife.03532] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 09/29/2014] [Indexed: 11/13/2022] Open
Abstract
PapC ushers are outer-membrane proteins enabling assembly and secretion of P pili in uropathogenic E. coli. Their translocation domain is a large β-barrel occluded by a plug domain, which is displaced to allow the translocation of pilus subunits across the membrane. Previous studies suggested that this gating mechanism is controlled by a β-hairpin and an α-helix. To investigate the role of these elements in allosteric signal communication, we developed a method combining evolutionary and molecular dynamics studies of the native translocation domain and mutants lacking the β-hairpin and/or the α-helix. Analysis of a hybrid residue interaction network suggests distinct regions (residue 'communities') within the translocation domain (especially around β12-β14) linking these elements, thereby modulating PapC gating. Antibiotic sensitivity and electrophysiology experiments on a set of alanine-substitution mutants confirmed functional roles for four of these communities. This study illuminates the gating mechanism of PapC ushers and its importance in maintaining outer-membrane permeability.
Collapse
Affiliation(s)
- Irene Farabella
- Institute of Structural and Molecular Biology, Birkbeck College and University College London, London, United Kingdom
| | - Thieng Pham
- Department of Biology and Biochemistry, University of Houston, Houston, United States
| | - Nadine S Henderson
- Department of Molecular Genetics and Microbiology, Center for Infectious Diseases, Stony Brook University, Stony Brook, United States
| | - Sebastian Geibel
- Institute of Structural and Molecular Biology, Birkbeck College and University College London, London, United Kingdom
| | - Gilles Phan
- Institute of Structural and Molecular Biology, Birkbeck College and University College London, London, United Kingdom
| | - David G Thanassi
- Department of Molecular Genetics and Microbiology, Center for Infectious Diseases, Stony Brook University, Stony Brook, United States
| | - Anne H Delcour
- Department of Biology and Biochemistry, University of Houston, Houston, United States
| | - Gabriel Waksman
- Institute of Structural and Molecular Biology, Birkbeck College and University College London, London, United Kingdom
| | - Maya Topf
- Institute of Structural and Molecular Biology, Birkbeck College and University College London, London, United Kingdom
| |
Collapse
|
85
|
Cafiso DS. Identifying and quantitating conformational exchange in membrane proteins using site-directed spin labeling. Acc Chem Res 2014; 47:3102-9. [PMID: 25152957 PMCID: PMC4204925 DOI: 10.1021/ar500228s] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Protein structures are not static but sample different conformations
over a range of amplitudes and time scales. These fluctuations may
involve relatively small changes in bond angles or quite large rearrangements
in secondary structure and tertiary fold. The equilibrium between
discrete structural substates on the microsecond to millisecond time
scale is sometimes termed conformational exchange. Protein dynamics
and conformational exchange are believed to provide the basis for
many important activities, such as protein–protein and protein–ligand
interactions, enzymatic activity and protein allostery; however, for
many proteins, the dynamics and conformational exchange that lead
to function are poorly defined. Spectroscopic methods, such
as NMR, are among the most important
methods to explore protein dynamics and conformational exchange; however,
they are difficult to implement in some systems and with some types
of exchange events. Site-directed spin labeling (SDSL) is an EPR based
approach that is particularly well-suited to high molecular-weight
systems such as membrane proteins. Because of the relatively fast
time scale for EPR spectroscopy, it is an excellent method to examine
exchange. Conformations that are in exchange are captured as distinct
populations in the EPR spectrum, and this feature when combined with
the use of methods that can shift the free energy of conformational
substates allows one to identify regions of proteins that are in dynamic
exchange. In addition, modern pulse EPR methods have the ability to
examine conformational heterogeneity, resolve discrete protein states,
and identify the substates in exchange. Protein crystallography
has provided high-resolution models for
a number of membrane proteins; but because of conformational exchange,
these models do not always reflect the structures that are present
when the protein is in a native bilayer environment. In the case of
the Escherichia coli vitamin B12 transporter,
BtuB, the energy coupling segment of this protein undergoes a substrate-dependent
unfolding, which acts to couple this outer-membrane protein to the
inner-membrane protein TonB. EPR spectroscopy demonstrates that the
energy coupling segment is in equilibrium between ordered and disordered
states, and that substrate binding shifts this equilibrium to favor
an unfolded state. However, in crystal structures of BtuB, this segment
is resolved and folded within the protein, and neither the presence
of this equilibrium nor the substrate-induced change is revealed.
This is a result of the solute environment and the crystal lattice,
both of which act to stabilize one conformational substate of the
transporter. Using SDSL, it can be shown that conformational
exchange is present
in other regions of BtuB and in other members of this transporter
family. Conformational exchange has also been examined in systems
such as the plasma membrane SNARE protein, syntaxin 1A, where dynamics
are controlled by regulatory proteins such as munc18. Regulating the
microsecond to millisecond time scale dynamics in the neuronal SNAREs
is likely to be a key feature that regulates assembly of the SNAREs
and neurotransmitter release.
Collapse
Affiliation(s)
- David S. Cafiso
- Department of Chemistry and Center for Membrane Biology, University of Virginia, Charlottesville, Virginia 22904-4319, United States
| |
Collapse
|
86
|
Bao R, Fordyce A, Chen YX, McVeigh A, Savarino SJ, Xia D. Structure of CfaA suggests a new family of chaperones essential for assembly of class 5 fimbriae. PLoS Pathog 2014; 10:e1004316. [PMID: 25122114 PMCID: PMC4133393 DOI: 10.1371/journal.ppat.1004316] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Accepted: 06/27/2014] [Indexed: 01/22/2023] Open
Abstract
Adhesive pili on the surface of pathogenic bacteria comprise polymerized pilin subunits and are essential for initiation of infections. Pili assembled by the chaperone-usher pathway (CUP) require periplasmic chaperones that assist subunit folding, maintain their stability, and escort them to the site of bioassembly. Until now, CUP chaperones have been classified into two families, FGS and FGL, based on the short and long length of the subunit-interacting loops between its F1 and G1 β-strands, respectively. CfaA is the chaperone for assembly of colonization factor antigen I (CFA/I) pili of enterotoxigenic E. coli (ETEC), a cause of diarrhea in travelers and young children. Here, the crystal structure of CfaA along with sequence analyses reveals some unique structural and functional features, leading us to propose a separate family for CfaA and closely related chaperones. Phenotypic changes resulting from mutations in regions unique to this chaperone family provide insight into their function, consistent with involvement of these regions in interactions with cognate subunits and usher proteins during pilus assembly.
Collapse
Affiliation(s)
- Rui Bao
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - April Fordyce
- Enteric Diseases Department, Infectious Diseases Directorate, Naval Medical Research Center, Silver Spring, Maryland, United States of America
| | - Yu-Xing Chen
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, People's Republic of China
| | - Annette McVeigh
- Enteric Diseases Department, Infectious Diseases Directorate, Naval Medical Research Center, Silver Spring, Maryland, United States of America
| | - Stephen J Savarino
- Enteric Diseases Department, Infectious Diseases Directorate, Naval Medical Research Center, Silver Spring, Maryland, United States of America; Department of Pediatrics, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
| | - Di Xia
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| |
Collapse
|
87
|
Salinas T, El Farouk-Ameqrane S, Ubrig E, Sauter C, Duchêne AM, Maréchal-Drouard L. Molecular basis for the differential interaction of plant mitochondrial VDAC proteins with tRNAs. Nucleic Acids Res 2014; 42:9937-48. [PMID: 25114051 PMCID: PMC4150812 DOI: 10.1093/nar/gku728] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In plants, the voltage-dependent anion-selective channel (VDAC) is a major component of a pathway involved in transfer RNA (tRNA) translocation through the mitochondrial outer membrane. However, the way in which VDAC proteins interact with tRNAs is still unknown. Potato mitochondria contain two major mitochondrial VDAC proteins, VDAC34 and VDAC36. These two proteins, composed of a N-terminal α-helix and of 19 β-strands forming a β-barrel structure, share 75% sequence identity. Here, using both northwestern and gel shift experiments, we report that these two proteins interact differentially with nucleic acids. VDAC34 binds more efficiently with tRNAs or other nucleic acids than VDAC36. To further identify specific features and critical amino acids required for tRNA binding, 21 VDAC34 mutants were constructed and analyzed by northwestern. This allowed us to show that the β-barrel structure of VDAC34 and the first 50 amino acids that contain the α-helix are essential for RNA binding. Altogether the work shows that during evolution, plant mitochondrial VDAC proteins have diverged so as to interact differentially with nucleic acids, and this may reflect their involvement in various specialized biological functions.
Collapse
Affiliation(s)
- Thalia Salinas
- Institut de Biologie Moléculaire des Plantes, UPR 2357 CNRS, associated with Strasbourg University, 12 rue du Général Zimmer 67084 Strasbourg cedex, France
| | - Samira El Farouk-Ameqrane
- Institut de Biologie Moléculaire des Plantes, UPR 2357 CNRS, associated with Strasbourg University, 12 rue du Général Zimmer 67084 Strasbourg cedex, France
| | - Elodie Ubrig
- Institut de Biologie Moléculaire des Plantes, UPR 2357 CNRS, associated with Strasbourg University, 12 rue du Général Zimmer 67084 Strasbourg cedex, France
| | - Claude Sauter
- Institut de Biologie Moléculaire et Cellulaire, UPR 9002 CNRS, associated with Strasbourg University, 15 rue René Descartes 67084 Strasbourg cedex, France
| | - Anne-Marie Duchêne
- Institut de Biologie Moléculaire des Plantes, UPR 2357 CNRS, associated with Strasbourg University, 12 rue du Général Zimmer 67084 Strasbourg cedex, France
| | - Laurence Maréchal-Drouard
- Institut de Biologie Moléculaire des Plantes, UPR 2357 CNRS, associated with Strasbourg University, 12 rue du Général Zimmer 67084 Strasbourg cedex, France
| |
Collapse
|
88
|
Geibel S, Waksman G. The molecular dissection of the chaperone–usher pathway. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1559-67. [DOI: 10.1016/j.bbamcr.2013.09.023] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Revised: 09/25/2013] [Accepted: 09/30/2013] [Indexed: 01/11/2023]
|
89
|
Lillington J, Geibel S, Waksman G. Reprint of "Biogenesis and adhesion of type 1 and P pili". Biochim Biophys Acta Gen Subj 2014; 1850:554-64. [PMID: 25063559 DOI: 10.1016/j.bbagen.2014.07.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 04/22/2014] [Accepted: 04/24/2014] [Indexed: 12/20/2022]
Abstract
BACKGROUND Uropathogenic Escherichia coli (UPEC) cause urinary tract infections (UTIs) in approximately 50% of women. These bacteria use type 1 and P pili for host recognition and attachment. These pili are assembled by the chaperone-usher pathway of pilus biogenesis. SCOPE OF REVIEW The review examines the biogenesis and adhesion of the UPEC type 1 and P pili. Particular emphasis is drawn to the role of the outer membrane usher protein. The structural properties of the complete pilus are also examined to highlight the strength and functionality of the final assembly. MAJOR CONCLUSIONS The usher orchestrates the sequential addition of pilus subunits in a defined order. This process follows a subunit-incorporation cycle which consists of four steps: recruitment at the usher N-terminal domain, donor-strand exchange with the previously assembled subunit, transfer to the usher C-terminal domains and translocation of the nascent pilus. Adhesion by the type 1 and P pili is strengthened by the quaternary structure of their rod sections. The rod is endowed with spring-like properties which provide mechanical resistance against urine flow. The distal adhesins operate differently from one another, targeting receptors in a specific manner. The biogenesis and adhesion of type 1 and P pili are being therapeutically targeted, and efforts to prevent pilus growth or adherence are described. GENERAL SIGNIFICANCE The combination of structural and biochemical study has led to the detailed mechanistic understanding of this membrane spanning nano-machine. This can now be exploited to design novel drugs able to inhibit virulence. This is vital in the present era of resurgent antibiotic resistance. This article is part of a Special Issue entitled Structural biochemistry and biophysics of membrane proteins.
Collapse
Affiliation(s)
- James Lillington
- Institute of Structural and Molecular Biology (ISMB), University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK
| | - Sebastian Geibel
- Institute of Structural and Molecular Biology (ISMB), University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK
| | - Gabriel Waksman
- Institute of Structural and Molecular Biology (ISMB), University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK.
| |
Collapse
|
90
|
Dong H, Xiang Q, Gu Y, Wang Z, Paterson NG, Stansfeld PJ, He C, Zhang Y, Wang W, Dong C. Structural basis for outer membrane lipopolysaccharide insertion. Nature 2014; 511:52-6. [DOI: 10.1038/nature13464] [Citation(s) in RCA: 195] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Accepted: 05/12/2014] [Indexed: 12/21/2022]
|
91
|
Lillington J, Geibel S, Waksman G. Biogenesis and adhesion of type 1 and P pili. Biochim Biophys Acta Gen Subj 2014; 1840:2783-93. [PMID: 24797039 DOI: 10.1016/j.bbagen.2014.04.021] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 04/22/2014] [Accepted: 04/24/2014] [Indexed: 01/22/2023]
Abstract
BACKGROUND Uropathogenic Escherichia coli (UPEC) cause urinary tract infections (UTIs) in approximately 50% of women. These bacteria use type 1 and P pili for host recognition and attachment. These pili are assembled by the chaperone-usher pathway of pilus biogenesis. SCOPE OF REVIEW The review examines the biogenesis and adhesion of the UPEC type 1 and P pili. Particular emphasis is drawn to the role of the outer membrane usher protein. The structural properties of the complete pilus are also examined to highlight the strength and functionality of the final assembly. MAJOR CONCLUSIONS The usher orchestrates the sequential addition of pilus subunits in a defined order. This process follows a subunit-incorporation cycle which consists of four steps: recruitment at the usher N-terminal domain, donor-strand exchange with the previously assembled subunit, transfer to the usher C-terminal domains and translocation of the nascent pilus. Adhesion by the type 1 and P pili is strengthened by the quaternary structure of their rod sections. The rod is endowed with spring-like properties which provide mechanical resistance against urine flow. The distal adhesins operate differently from one another, targeting receptors in a specific manner. The biogenesis and adhesion of type 1 and P pili are being therapeutically targeted, and efforts to prevent pilus growth or adherence are described. GENERAL SIGNIFICANCE The combination of structural and biochemical study has led to the detailed mechanistic understanding of this membrane spanning nano-machine. This can now be exploited to design novel drugs able to inhibit virulence. This is vital in the present era of resurgent antibiotic resistance. This article is part of a Special Issue entitled Structural biochemistry and biophysics of membrane proteins.
Collapse
Affiliation(s)
- James Lillington
- Institute of Structural and Molecular Biology (ISMB), University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK
| | - Sebastian Geibel
- Institute of Structural and Molecular Biology (ISMB), University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK
| | - Gabriel Waksman
- Institute of Structural and Molecular Biology (ISMB), University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK.
| |
Collapse
|
92
|
Van Gerven N, Goyal P, Vandenbussche G, De Kerpel M, Jonckheere W, De Greve H, Remaut H. Secretion and functional display of fusion proteins through the curli biogenesis pathway. Mol Microbiol 2014; 91:1022-35. [PMID: 24417346 DOI: 10.1111/mmi.12515] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/09/2014] [Indexed: 01/04/2023]
Abstract
Curli are functional amyloids expressed as fibres on the surface of Enterobacteriaceae. Contrary to the protein misfolding events associated with pathogenic amyloidosis, curli are the result of a dedicated biosynthetic pathway. A specialized transporter in the outer membrane, CsgG, operates in conjunction with the two accessory proteins CsgE and CsgF to secrete curlin subunits to the extracellular surface, where they nucleate into cross-beta strand fibres. Here we investigate the substrate tolerance of the CsgG transporter and the capability of heterologous sequences to be built into curli fibres. Non-native polypeptides ranging up to at least 260 residues were exported when fused to the curli subunit CsgA. Secretion efficiency depended on the folding properties of the passenger sequences, with substrates exceeding an approximately 2 nm transverse diameter blocking passage through the transport channel. Secretion of smaller passengers was compatible with prior DsbA-mediated disulphide bridge formation in the fusion partner, indicating that CsgG is capable of translocating non-linear polypeptide stretches. Using fusions we further demonstrate the exported or secreted heterologous passenger proteins can attain their native, active fold, establishing curli biogenesis pathway as a platform for the secretion and surface display of small heterologous proteins.
Collapse
Affiliation(s)
- Nani Van Gerven
- Structural & Molecular Microbiology, Structural Biology Research Center, VIB, Pleinlaan 2, 1050, Brussels, Belgium; Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium
| | | | | | | | | | | | | |
Collapse
|
93
|
Gouin SG, Roos G, Bouckaert J. Discovery and Application of FimH Antagonists. TOPICS IN MEDICINAL CHEMISTRY 2014. [DOI: 10.1007/7355_2014_52] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
|
94
|
Abstract
Most biophysical experiments require protein samples of high quality and accurately determined concentration. This chapter attempts to compile basic information on the most common methods to assess the purity, dispersity, and stability of protein samples. It also reminds of methods to measure protein concentration and of their limits. The idea is to make aware and remind of the range of methods available and of commonly overlooked pitfalls. The aim is to enable experimenters to fully characterize their preparations of soluble or membrane proteins and gain reliable and reproducible results from their experimental work.
Collapse
Affiliation(s)
- Tina Daviter
- ISMB Biophysics Centre, Institute of Structural and Molecular Biology, Birkbeck, University of London, London, UK
| | | |
Collapse
|
95
|
Lo AWH, Van de Water K, Gane PJ, Chan AWE, Steadman D, Stevens K, Selwood DL, Waksman G, Remaut H. Suppression of type 1 pilus assembly in uropathogenic Escherichia coli by chemical inhibition of subunit polymerization. J Antimicrob Chemother 2013; 69:1017-26. [PMID: 24324225 PMCID: PMC3956373 DOI: 10.1093/jac/dkt467] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Objectives To identify and to characterize small-molecule inhibitors that target the subunit polymerization of the type 1 pilus assembly in uropathogenic Escherichia coli (UPEC). Methods Using an SDS–PAGE-based assay, in silico pre-filtered small-molecule compounds were screened for specific inhibitory activity against the critical subunit polymerization step of the chaperone–usher pathway during pilus biogenesis. The biological activity of one of the compounds was validated in assays monitoring UPEC type 1 pilus biogenesis, type 1 pilus-dependent biofilm formation and adherence to human bladder epithelial cells. The time dependence of the in vivo inhibitory activity and the overall effect of the compound on UPEC growth were determined. Results N-(4-chloro-phenyl)-2-{5-[4-(pyrrolidine-1-sulfonyl)-phenyl]-[1,3,4]oxadiazol-2-yl sulfanyl}-acetamide (AL1) inhibited in vitro pilus subunit polymerization. In bacterial cultures, AL1 disrupted UPEC type 1 pilus biogenesis and pilus-dependent biofilm formation, and resulted in the reduction of bacterial adherence to human bladder epithelial cells, without affecting bacterial cell growth. Bacterial exposure to the inhibitor led to an almost instantaneous loss of type 1 pili. Conclusions We have identified and characterized a small molecule that interferes with the assembly of type 1 pili. The molecule targets the polymerization step during the subunit incorporation cycle of the chaperone–usher pathway. Our discovery provides new insight into the design and development of novel anti-virulence therapies targeting key virulence factors of bacterial pathogens.
Collapse
Affiliation(s)
- Alvin W H Lo
- Structural and Molecular Microbiology, VIB Department of Structural Biology, VIB, Pleinlaan 2, 1050 Brussels, Belgium
| | | | | | | | | | | | | | | | | |
Collapse
|
96
|
Molecular basis of usher pore gating in Escherichia coli pilus biogenesis. Proc Natl Acad Sci U S A 2013; 110:20741-6. [PMID: 24297893 DOI: 10.1073/pnas.1320528110] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Extracellular fibers called chaperone-usher pathway pili are critical virulence factors in a wide range of Gram-negative pathogenic bacteria that facilitate binding and invasion into host tissues and mediate biofilm formation. Chaperone-usher pathway ushers, which catalyze pilus assembly, contain five functional domains: a 24-stranded transmembrane β-barrel translocation domain (TD), a β-sandwich plug domain (PLUG), an N-terminal periplasmic domain, and two C-terminal periplasmic domains (CTD1 and 2). Pore gating occurs by a mechanism whereby the PLUG resides stably within the TD pore when the usher is inactive and then upon activation is translocated into the periplasmic space, where it functions in pilus assembly. Using antibiotic sensitivity and electrophysiology experiments, a single salt bridge was shown to function in maintaining the PLUG in the TD channel of the P pilus usher PapC, and a loop between the 12th and 13th beta strands of the TD (β12-13 loop) was found to facilitate pore opening. Mutation of the β12-13 loop resulted in a closed PapC pore, which was unable to efficiently mediate pilus assembly. Deletion of the PapH terminator/anchor resulted in increased OM permeability, suggesting a role for the proper anchoring of pili in retaining OM integrity. Further, we introduced cysteine residues in the PLUG and N-terminal periplasmic domains that resulted in a FimD usher with a greater propensity to exist in an open conformation, resulting in increased OM permeability but no loss in type 1 pilus assembly. These studies provide insights into the molecular basis of usher pore gating and its roles in pilus biogenesis and OM permeability.
Collapse
|
97
|
Intramolecular donor strand complementation in the E. coli type 1 pilus subunit FimA explains the existence of FimA monomers as off-pathway products of pilus assembly that inhibit host cell apoptosis. J Mol Biol 2013; 426:542-9. [PMID: 24184277 DOI: 10.1016/j.jmb.2013.10.029] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 10/04/2013] [Accepted: 10/22/2013] [Indexed: 11/22/2022]
Abstract
Type 1 pili are filamentous organelles mediating the attachment of uropathogenic Escherichia coli to epithelial cells of host organisms. The helical pilus rod consists of up to 3000 copies of the main structural subunit FimA that interact via donor strand complementation, where the incomplete Ig-like fold of FimA is completed by insertion of the N-terminal extension (donor strand) of the following FimA subunit. Recently, it was shown that FimA also exists in a monomeric, assembly-incompetent form and that FimA monomers act as inhibitors of apoptosis in infected host cells. Here we present the NMR structure of monomeric wild-type FimA with its natural N-terminal donor strand complementing the Ig fold. Compared to FimA subunits in the assembled pilus, intramolecular self-complementation in the monomer stabilizes the FimA fold with significantly less interactions, and the natural FimA donor strand is inserted in the opposite orientation. In addition, we show that a motif of two glycine residues in the FimA donor strand, separated by five residues, is the prerequisite of the alternative, parallel donor strand insertion mechanism in the FimA monomer and that this motif is preserved in FimA homologs of many enteroinvasive pathogens. We conclude that FimA is a unique case of a protein with alternative, functionally relevant folding possibilities, with the FimA polymer forming the highly stable pilus rod and the FimA monomer promoting pathogen propagation by apoptosis suppression of infected epithelial target cells.
Collapse
|
98
|
Garnett JA, Matthews S. Interactions in bacterial biofilm development: a structural perspective. Curr Protein Pept Sci 2013; 13:739-55. [PMID: 23305361 PMCID: PMC3601411 DOI: 10.2174/138920312804871166] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Revised: 07/16/2012] [Accepted: 08/03/2012] [Indexed: 11/24/2022]
Abstract
A community-based life style is the normal mode of growth and survival for many bacterial species. These cellular accretions or biofilms are initiated upon recognition of solid phases by cell surface exposed adhesive moieties. Further cell-cell interactions, cell signalling and bacterial replication leads to the establishment of dense populations encapsulated in a mainly self-produced extracellular matrix; this comprises a complex mixture of macromolecules. These fascinating architectures protect the inhabitants from radiation damage, dehydration, pH fluctuations and antimicrobial compounds. As such they can cause bacterial persistence in disease and problems in industrial applications. In this review we discuss the current understandings of these initial biofilm-forming processes based on structural data. We also briefly describe latter biofilm maturation and dispersal events, which although lack high-resolution insights, are the present focus for many structural biologists working in this field. Finally we give an overview of modern techniques aimed at preventing and disrupting problem biofilms.
Collapse
Affiliation(s)
- James A Garnett
- Centre for Structural Biology, Department of Life Sciences, Imperial College London, South Kensington, London SW7 2AZ, UK
| | | |
Collapse
|
99
|
Razzaghi S, Brooks EK, Bordignon E, Hubbell WL, Yulikov M, Jeschke G. EPR relaxation-enhancement-based distance measurements on orthogonally spin-labeled T4-lysozyme. Chembiochem 2013; 14:1883-90. [PMID: 23775845 PMCID: PMC3804414 DOI: 10.1002/cbic.201300165] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Indexed: 12/20/2022]
Abstract
Lanthanide-induced enhancement of the longitudinal relaxation of nitroxide radicals in combination with orthogonal site-directed spin labeling is presented as a systematic distance measurement method intended for studies of bio-macromolecules and bio-macromolecular complexes. The approach is tested on a water-soluble protein (T4-lysozyme) for two different commercially available lanthanide labels, and complemented by previously reported data on a membrane-inserted polypeptide. Single temperature measurements are shown to be sufficient for reliable distance determination, with an upper measurable distance limit of about 5-6 nm. The extracted averaged distances represent the closest approach in Ln(III) -nitroxide distance distributions. Studies of conformational changes and of bio-macromolecule association-dissociation are proposed as possible application area of the relaxation-enhancement-based distance measurements.
Collapse
Affiliation(s)
| | - Evan K. Brooks
- Jules Stein Eye Institute and the Department of Chemistry and Biochemistry, University of California, Los Angeles, USA
| | | | - Wayne L. Hubbell
- Jules Stein Eye Institute and the Department of Chemistry and Biochemistry, University of California, Los Angeles, USA
| | - Maxim Yulikov
- Laboratory of Physical Chemistry, ETH Zurich, Switzerland
| | - Gunnar Jeschke
- Laboratory of Physical Chemistry, ETH Zurich, Switzerland
| |
Collapse
|
100
|
Positively selected FimH residues enhance virulence during urinary tract infection by altering FimH conformation. Proc Natl Acad Sci U S A 2013; 110:15530-7. [PMID: 24003161 DOI: 10.1073/pnas.1315203110] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Chaperone-usher pathway pili are a widespread family of extracellular, Gram-negative bacterial fibers with important roles in bacterial pathogenesis. Type 1 pili are important virulence factors in uropathogenic Escherichia coli (UPEC), which cause the majority of urinary tract infections (UTI). FimH, the type 1 adhesin, binds mannosylated glycoproteins on the surface of human and murine bladder cells, facilitating bacterial colonization, invasion, and formation of biofilm-like intracellular bacterial communities. The mannose-binding pocket of FimH is invariant among UPEC. We discovered that pathoadaptive alleles of FimH with variant residues outside the binding pocket affect FimH-mediated acute and chronic pathogenesis of two commonly studied UPEC strains, UTI89 and CFT073. In vitro binding studies revealed that, whereas all pathoadaptive variants tested displayed the same high affinity for mannose when bound by the chaperone FimC, affinities varied when FimH was incorporated into pilus tip-like, FimCGH complexes. Structural studies have shown that FimH adopts an elongated conformation when complexed with FimC, but, when incorporated into the pilus tip, FimH can adopt a compact conformation. We hypothesize that the propensity of FimH to adopt the elongated conformation in the tip corresponds to its mannose binding affinity. Interestingly, FimH variants, which maintain a high-affinity conformation in the FimCGH tip-like structure, were attenuated during chronic bladder infection, implying that FimH's ability to switch between conformations is important in pathogenesis. Our studies argue that positively selected residues modulate fitness during UTI by affecting FimH conformation and function, providing an example of evolutionary tuning of structural dynamics impacting in vivo survival.
Collapse
|