51
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Yang YH, Jiang YL, Zhang J, Wang L, Bai XH, Zhang SJ, Ren YM, Li N, Zhang YH, Zhang Z, Gong Q, Mei Y, Xue T, Zhang JR, Chen Y, Zhou CZ. Structural insights into SraP-mediated Staphylococcus aureus adhesion to host cells. PLoS Pathog 2014; 10:e1004169. [PMID: 24901708 PMCID: PMC4047093 DOI: 10.1371/journal.ppat.1004169] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Accepted: 04/22/2014] [Indexed: 11/18/2022] Open
Abstract
Staphylococcus aureus, a Gram-positive bacterium causes a number of devastating human diseases, such as infective endocarditis, osteomyelitis, septic arthritis and sepsis. S. aureus SraP, a surface-exposed serine-rich repeat glycoprotein (SRRP), is required for the pathogenesis of human infective endocarditis via its ligand-binding region (BR) adhering to human platelets. It remains unclear how SraP interacts with human host. Here we report the 2.05 Å crystal structure of the BR of SraP, revealing an extended rod-like architecture of four discrete modules. The N-terminal legume lectin-like module specifically binds to N-acetylneuraminic acid. The second module adopts a β-grasp fold similar to Ig-binding proteins, whereas the last two tandem repetitive modules resemble eukaryotic cadherins but differ in calcium coordination pattern. Under the conditions tested, small-angle X-ray scattering and molecular dynamic simulation indicated that the three C-terminal modules function as a relatively rigid stem to extend the N-terminal lectin module outwards. Structure-guided mutagenesis analyses, in addition to a recently identified trisaccharide ligand of SraP, enabled us to elucidate that SraP binding to sialylated receptors promotes S. aureus adhesion to and invasion into host epithelial cells. Our findings have thus provided novel structural and functional insights into the SraP-mediated host-pathogen interaction of S. aureus.
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Affiliation(s)
- Yi-Hu Yang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei Anhui, People's Republic of China
| | - Yong-Liang Jiang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei Anhui, People's Republic of China
| | - Juan Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei Anhui, People's Republic of China
| | - Lei Wang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei Anhui, People's Republic of China
| | - Xiao-Hui Bai
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei Anhui, People's Republic of China
| | - Shi-Jie Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei Anhui, People's Republic of China
| | - Yan-Min Ren
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei Anhui, People's Republic of China
| | - Na Li
- Shanghai Institute of Biochemistry and Cell Biology, Shanghai, China
| | - Yong-Hui Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei Anhui, People's Republic of China
| | - Zhiyong Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei Anhui, People's Republic of China
| | - Qingguo Gong
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei Anhui, People's Republic of China
| | - Yide Mei
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei Anhui, People's Republic of China
| | - Ting Xue
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei Anhui, People's Republic of China
| | - Jing-Ren Zhang
- Center for Infectious Disease Research, School of Medicine, Tsinghua University, Beijing, People's Republic of China
| | - Yuxing Chen
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei Anhui, People's Republic of China
- * E-mail: (YC); (CZZ)
| | - Cong-Zhao Zhou
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei Anhui, People's Republic of China
- * E-mail: (YC); (CZZ)
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52
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Abstract
Adequate salivary secretion is crucial to both oral and general health, since it provides a complex milieu for support of the microbial populations of the mouth, while at the same time containing antimicrobial products that help control these microbial populations. This paper summarizes several aspects of salivary component function, gland secretion mechanisms, and immunopathogenesis as related to oral health and disease. Salivary components mediate microbial attachment to oral surfaces, and also interact with planktonic microbial surfaces to facilitate agglutination and elimination of pathogens from the oral cavity. Adhesive interactions are often mediated by lectin-like bacterial proteins that bind to glycan motifs on salivary glycoproteins. An important salivary antimicrobial protein is histatin 5 (Hst 5), which shows potent and selective antifungal activity and also susceptibility to proteolytic degradation. Coupling of Hst 5 with the carrier molecule spermidine significantly enhanced killing of C. albicans and resistance to proteolytic degradation, compared with the parent peptide. Loss of salivary secretion may be caused by disorders such as Sjögren's syndrome (SS) or ectodermal dysplasia, or may be a side-effect of radiation therapy. Two new approaches to the treatment of salivary gland dysfunction include the use of resolvins and the creation of differentiated acinar structures to construct an artificial salivary gland. B-cells contribute to the pathogenesis of SS by releasing cytokines and autoantibodies and by influencing T-cell differentiation. CXCL13, a potent B-cell chemokine associated with autoimmune diseases, is elevated locally and systemically in SS and may represent a novel biomarker or therapeutic target in the management and treatment of SS.
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Affiliation(s)
- O.J. Baker
- Department of Oral Biology, School of Dental
Medicine, University at Buffalo, The State University of New York, Buffalo, NY 14214-309
USA
| | - M. Edgerton
- Department of Oral Biology, School of Dental
Medicine, University at Buffalo, The State University of New York, Buffalo, NY 14214-309
USA
| | - J.M. Kramer
- Department of Oral Biology, School of Dental
Medicine, University at Buffalo, The State University of New York, Buffalo, NY 14214-309
USA
| | - S. Ruhl
- Department of Oral Biology, School of Dental
Medicine, University at Buffalo, The State University of New York, Buffalo, NY 14214-309
USA
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53
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Wang NY, Patras KA, Seo HS, Cavaco CK, Rösler B, Neely MN, Sullam PM, Doran KS. Group B streptococcal serine-rich repeat proteins promote interaction with fibrinogen and vaginal colonization. J Infect Dis 2014; 210:982-91. [PMID: 24620021 DOI: 10.1093/infdis/jiu151] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Group B streptococcus (GBS) can cause severe disease in susceptible hosts, including newborns, pregnant women, and the elderly. GBS serine-rich repeat (Srr) surface glycoproteins are important adhesins/invasins in multiple host tissues, including the vagina. However, exact molecular mechanisms contributing to their importance in colonization are unknown. We have recently determined that Srr proteins contain a fibrinogen-binding region (BR) and hypothesize that Srr-mediated fibrinogen binding may contribute to GBS cervicovaginal colonization. In this study, we observed that fibrinogen enhanced wild-type GBS attachment to cervical and vaginal epithelium, and that this was dependent on Srr1. Moreover, purified Srr1-BR peptide bound directly to host cells, and peptide administration in vivo reduced GBS recovery from the vaginal tract. Furthermore, a GBS mutant strain lacking only the Srr1 "latching" domain exhibited decreased adherence in vitro and decreased persistence in a mouse model of GBS vaginal colonization, suggesting the importance of Srr-fibrinogen interactions in the female reproductive tract.
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Affiliation(s)
- Nai-Yu Wang
- Department of Biology and Center for Microbial Sciences, San Diego State University
| | - Kathryn A Patras
- Department of Biology and Center for Microbial Sciences, San Diego State University
| | - Ho Seong Seo
- Division of Infectious Diseases, Veteran Affairs Medical Center and the University of California San Francisco, California Radiation Biotechnology Research Division, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Republic of Korea
| | - Courtney K Cavaco
- Department of Biology and Center for Microbial Sciences, San Diego State University
| | - Berenice Rösler
- Department of Biology and Center for Microbial Sciences, San Diego State University
| | - Melody N Neely
- Department of Immunology and Microbiology, School of Medicine, Wayne State University, Detroit, Michigan
| | - Paul M Sullam
- Division of Infectious Diseases, Veteran Affairs Medical Center and the University of California San Francisco, California
| | - Kelly S Doran
- Department of Biology and Center for Microbial Sciences, San Diego State University Department of Pediatrics, University of California San Diego School of Medicine, La Jolla
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54
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Schulte T, Löfling J, Mikaelsson C, Kikhney A, Hentrich K, Diamante A, Ebel C, Normark S, Svergun D, Henriques-Normark B, Achour A. The basic keratin 10-binding domain of the virulence-associated pneumococcal serine-rich protein PsrP adopts a novel MSCRAMM fold. Open Biol 2014; 4:130090. [PMID: 24430336 PMCID: PMC3909270 DOI: 10.1098/rsob.130090] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Streptococcus pneumoniae is a major human pathogen, and a leading cause of disease and death worldwide. Pneumococcal invasive disease is triggered by initial asymptomatic colonization of the human upper respiratory tract. The pneumococcal serine-rich repeat protein (PsrP) is a lung-specific virulence factor whose functional binding region (BR) binds to keratin-10 (KRT10) and promotes pneumococcal biofilm formation through self-oligomerization. We present the crystal structure of the KRT10-binding domain of PsrP (BR187–385) determined to 2.0 Å resolution. BR187–385 adopts a novel variant of the DEv-IgG fold, typical for microbial surface components recognizing adhesive matrix molecules adhesins, despite very low sequence identity. An extended β-sheet on one side of the compressed, two-sided barrel presents a basic groove that possibly binds to the acidic helical rod domain of KRT10. Our study also demonstrates the importance of the other side of the barrel, formed by extensive well-ordered loops and stabilized by short β-strands, for interaction with KRT10.
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Affiliation(s)
- Tim Schulte
- Science for Life Laboratory, Center for Infectious Medicine (CIM), Department of Medicine, Karolinska University Hospital Huddinge, Karolinska Institutet Science Park, Tomtebodavägen 23A Solna, Stockholm 17165, Sweden
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55
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Seo HS, Minasov G, Seepersaud R, Doran KS, Dubrovska I, Shuvalova L, Anderson WF, Iverson TM, Sullam PM. Characterization of fibrinogen binding by glycoproteins Srr1 and Srr2 of Streptococcus agalactiae. J Biol Chem 2013; 288:35982-96. [PMID: 24165132 PMCID: PMC3861647 DOI: 10.1074/jbc.m113.513358] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The serine-rich repeat glycoproteins of Gram-positive bacteria comprise a large family of cell wall proteins. Streptococcus agalactiae (group B streptococcus, GBS) expresses either Srr1 or Srr2 on its surface, depending on the strain. Srr1 has recently been shown to bind fibrinogen, and this interaction contributes to the pathogenesis of GBS meningitis. Although strains expressing Srr2 appear to be hypervirulent, no ligand for this adhesin has been described. We now demonstrate that Srr2 also binds human fibrinogen and that this interaction promotes GBS attachment to endothelial cells. Recombinant Srr1 and Srr2 bound fibrinogen in vitro, with affinities of KD = 2.1 × 10−5 and 3.7 × 10−6m, respectively, as measured by surface plasmon resonance spectroscopy. The binding site for Srr1 and Srr2 was localized to tandem repeats 6–8 of the fibrinogen Aα chain. The structures of both the Srr1 and Srr2 binding regions were determined and, in combination with mutagenesis studies, suggest that both Srr1 and Srr2 interact with a segment of these repeats via a “dock, lock, and latch” mechanism. Moreover, properties of the latch region may account for the increased affinity between Srr2 and fibrinogen. Together, these studies identify how greater affinity of Srr2 for fibrinogen may contribute to the increased virulence associated with Srr2-expressing strains.
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Affiliation(s)
- Ho Seong Seo
- From the Division of Infectious Diseases, Veterans Affairs Medical Center, University of California at San Francisco and the Northern California Institute for Research and Education, San Francisco, California 94121
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56
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Muller YA. Unexpected features in the Protein Data Bank entries 3qd1 and 4i8e: the structural description of the binding of the serine-rich repeat adhesin GspB to host cell carbohydrate receptor is not a solved issue. Acta Crystallogr Sect F Struct Biol Cryst Commun 2013; 69:1071-6. [PMID: 24100551 PMCID: PMC3792659 DOI: 10.1107/s1744309113014383] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Accepted: 05/24/2013] [Indexed: 11/10/2022]
Abstract
The structure of a complex between a fragment of the adhesin GspB from Streptococcus gordonii and a disaccharide (PDB entries 3qd1 and 4i8e) has recently been proposed to identify the binding site for the sialyl-T antigen recognized by GspB. This structure exhibits numerous unrealistic and unusual features such as an excessive number of van der Waals clashes and a lack of correlation between atomic structure and experimental electron density. Here, it is shown that the crystallographic data can be fully explained by an alternative model, namely replacing the disaccharide with a buffer molecule. The conclusion is that the experimental data are likely to contain no information regarding the carbohydrate receptor binding site in GspB or the interaction of GspB with host cell receptors.
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Affiliation(s)
- Yves A. Muller
- Lehrstuhl für Biotechnik, Department of Biology, Friedrich-Alexander University Erlangen-Nuremberg, Henkestrasse 91, 91052 Erlangen, Germany
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57
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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.
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Affiliation(s)
- James A Garnett
- Centre for Structural Biology, Department of Life Sciences, Imperial College London, South Kensington, London SW7 2AZ, UK
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58
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Nydegger UE, Risch L. Selected topics of the 4th International Cooperative Study Group meeting on immune thrombocytopenia revisited. Semin Hematol 2013; 50 Suppl 1:S3-9. [PMID: 23664513 DOI: 10.1053/j.seminhematol.2013.03.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The Intercontinental Cooperative immune thrombocytopenia (ITP) Study Group (ICIS) held its 4th Expert Meeting in September 2012 in Montreux, Switzerland. The program reunited researchers and clinicians from all over the globe and was organized with lectures and seminars for real-time exchange of latest information. Platelets target victims of autoimmune disease on their own, participating under physiological conditions in the immune network; these small cells are more immunologically savvy than previously thought. Currently, researchers focus their attention on regulatory T and regulatory B cells, ie, cells that might have a decisive impact on how ITP spontaneously resolves or evolves into chronic disease. Diagnostic criteria and prognosis are increasingly benefiting from molecular biological tests, and therapy has evolved with the availability of biosimilar agents and recombinant hormones or blockers of their receptors.
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59
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Nylander Å, Svensäter G, Senadheera DB, Cvitkovitch DG, Davies JR, Persson K. Structural and functional analysis of the N-terminal domain of the Streptococcus gordonii adhesin Sgo0707. PLoS One 2013; 8:e63768. [PMID: 23691093 PMCID: PMC3656908 DOI: 10.1371/journal.pone.0063768] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Accepted: 04/05/2013] [Indexed: 12/02/2022] Open
Abstract
The commensal Streptococcus gordonii expresses numerous surface adhesins with which it interacts with other microorganisms, host cells and salivary proteins to initiate dental plaque formation. However, this Gram-positive bacterium can also spread to non-oral sites such as the heart valves and cause infective endocarditis. One of its surface adhesins, Sgo0707, is a large protein composed of a non-repetitive N-terminal region followed by several C-terminal repeat domains and a cell wall sorting motif. Here we present the crystal structure of the Sgo0707 N-terminal domains, refined to 2.1 Å resolution. The model consists of two domains, N1 and N2. The largest domain, N1, comprises a putative binding cleft with a single cysteine located in its centre and exhibits an unexpected structural similarity to the variable domains of the streptococcal Antigen I/II adhesins. The N2-domain has an IgG-like fold commonly found among Gram-positive surface adhesins. Binding studies performed on S. gordonii wild-type and a Sgo0707 deficient mutant show that the Sgo0707 adhesin is involved in binding to type-1 collagen and to oral keratinocytes.
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Affiliation(s)
- Åsa Nylander
- Department of Odontology, Division of Oral Microbiology, Umeå University, Umeå, Sweden
| | - Gunnel Svensäter
- Department of Oral Biology, Faculty of Odontology, Malmö University, Malmö, Sweden
| | | | | | - Julia R. Davies
- Department of Oral Biology, Faculty of Odontology, Malmö University, Malmö, Sweden
| | - Karina Persson
- Department of Chemistry, Umeå University, Umeå, Sweden
- * E-mail:
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60
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Pozharski E, Weichenberger CX, Rupp B. Techniques, tools and best practices for ligand electron-density analysis and results from their application to deposited crystal structures. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2013; 69:150-67. [PMID: 23385452 DOI: 10.1107/s0907444912044423] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Accepted: 10/26/2012] [Indexed: 11/10/2022]
Abstract
As a result of substantial instrumental automation and the continuing improvement of software, crystallographic studies of biomolecules are conducted by non-experts in increasing numbers. While improved validation almost ensures that major mistakes in the protein part of structure models are exceedingly rare, in ligand-protein complex structures, which in general are most interesting to the scientist, ambiguous ligand electron density is often difficult to interpret and the modelled ligands are generally more difficult to properly validate. Here, (i) the primary technical reasons and potential human factors leading to problems in ligand structure models are presented; (ii) the most common categories of building errors or overinterpretation are classified; (iii) a few instructive and specific examples are discussed in detail, including an electron-density-based analysis of ligand structures that do not contain any ligands; (iv) means of avoiding such mistakes are suggested and the implications for database validity are discussed and (v) a user-friendly software tool that allows non-expert users to conveniently inspect ligand density is provided.
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Affiliation(s)
- Edwin Pozharski
- Department of Pharmaceutical Sciences, University of Maryland, Baltimore, MD, USA.
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61
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Differential localization of the streptococcal accessory sec components and implications for substrate export. J Bacteriol 2012. [PMID: 23204472 DOI: 10.1128/jb.01742-12] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The accessory Sec system of Streptococcus gordonii is comprised of SecY2, SecA2, and five proteins (Asp1 through -5) that are required for the export of a serine-rich glycoprotein, GspB. We have previously shown that a number of the Asps interact with GspB, SecA2, or each other. To further define the roles of these Asps in export, we examined their subcellular localization in S. gordonii and in Escherichia coli expressing the streptococcal accessory Sec system. In particular, we assessed how the locations of these accessory Sec proteins were altered by the presence of other components. Using fluorescence microscopy, we found in E. coli that SecA2 localized within multiple foci at the cell membrane, regardless of whether other accessory Sec proteins were expressed. Asp2 alone localized to the cell poles but formed a similar punctate pattern at the membrane when SecA2 was present. Asp1 and Asp3 localized diffusely in the cytosol when expressed alone or with SecA2. However, these proteins redistributed to the membrane in a punctate arrangement when all of the accessory Sec components were present. Cell fractionation studies with S. gordonii further corroborated these microscopy results. Collectively, these findings indicate that Asp1 to -3 are not integral membrane proteins that form structural parts of the translocation channel. Instead, SecA2 serves as a docking site for Asp2, which in turn attracts a complex of Asp1 and Asp3 to the membrane. These protein interactions may be important for the trafficking of GspB to the cell membrane and its subsequent translocation.
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62
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Seo HS, Mu R, Kim BJ, Doran KS, Sullam PM. Binding of glycoprotein Srr1 of Streptococcus agalactiae to fibrinogen promotes attachment to brain endothelium and the development of meningitis. PLoS Pathog 2012; 8:e1002947. [PMID: 23055927 PMCID: PMC3464228 DOI: 10.1371/journal.ppat.1002947] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Accepted: 08/20/2012] [Indexed: 12/11/2022] Open
Abstract
The serine-rich repeat glycoprotein Srr1 of Streptococcus agalactiae (GBS) is thought to be an important adhesin for the pathogenesis of meningitis. Although expression of Srr1 is associated with increased binding to human brain microvascular endothelial cells (hBMEC), the molecular basis for this interaction is not well defined. We now demonstrate that Srr1 contributes to GBS attachment to hBMEC via the direct interaction of its binding region (BR) with human fibrinogen. When assessed by Far Western blotting, Srr1 was the only protein in GBS extracts that bound fibrinogen. Studies using recombinant Srr1-BR and purified fibrinogen in vitro confirmed a direct protein-protein interaction. Srr1-BR binding was localized to amino acids 283–410 of the fibrinogen Aα chain. Structural predictions indicated that the conformation of Srr1-BR is likely to resemble that of SdrG and other related staphylococcal proteins that bind to fibrinogen through a “dock, lock, and latch” mechanism (DLL). Deletion of the predicted latch domain of Srr1-BR abolished the interaction of the BR with fibrinogen. In addition, a mutant GBS strain lacking the latch domain exhibited reduced binding to hBMEC, and was significantly attenuated in an in vivo model of meningitis. These results indicate that Srr1 can bind fibrinogen directly likely through a DLL mechanism, which has not been described for other streptococcal adhesins. This interaction was important for the pathogenesis of GBS central nervous system invasion and subsequent disease progression. Streptococcus agalactiae (Group B streptococcus, GBS) is a leading cause of meningitis in newborns and infants. This life-threatening infection of the brain and surrounding tissues continues to result in a high incidence of morbidity and mortality, despite antibiotic therapy. A key factor in disease production is the ability of this organism to invade the central nervous system, via the bloodstream. We now report that a GBS surface protein called Srr1 binds fibrinogen, a major protein in human blood. This interaction enhances the attachment of GBS to brain vascular endothelial cells, and contributes to the development of meningitis. A mutation in Srr1 that specifically disrupted binding to fibrinogen significantly reduced GBS attachment to brain endothelium, and markedly reduced virulence in an in vivo model of GBS disease. These studies have identified a new mechanism by which Srr1 contributes to GBS invasion of the central nervous system and may provide a basis for novel therapies targeting Srr1 binding.
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Affiliation(s)
- Ho Seong Seo
- Division of Infectious Diseases, Veterans Affairs Medical Center and the University of California, San Francisco, California, United States of America
| | - Rong Mu
- Department of Biology and Center for Microbial Sciences, San Diego State University, San Diego, California, United States of America
| | - Brandon J. Kim
- Department of Biology and Center for Microbial Sciences, San Diego State University, San Diego, California, United States of America
| | - Kelly S. Doran
- Department of Biology and Center for Microbial Sciences, San Diego State University, San Diego, California, United States of America
- Department of Pediatrics, University of California at San Diego, School of Medicine, La Jolla, California, United States of America
| | - Paul M. Sullam
- Division of Infectious Diseases, Veterans Affairs Medical Center and the University of California, San Francisco, California, United States of America
- * E-mail:
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63
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Lizcano A, Sanchez CJ, Orihuela CJ. A role for glycosylated serine-rich repeat proteins in gram-positive bacterial pathogenesis. Mol Oral Microbiol 2012; 27:257-69. [PMID: 22759311 DOI: 10.1111/j.2041-1014.2012.00653.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Bacterial attachment to host surfaces is a pivotal event in the biological and infectious processes of both commensal and pathogenic bacteria, respectively. Serine-rich repeat proteins (SRRPs) are a family of adhesins in Gram-positive bacteria that mediate attachment to a variety of host and bacterial surfaces. As such, they contribute towards a wide-range of diseases including sub-acute bacterial endocarditis, community-acquired pneumonia, and meningitis. SRRPs are unique in that they are glycosylated, require a non-canonical Sec-translocase for transport, and are largely composed of a domain containing hundreds of alternating serine residues. These serine-rich repeats are thought to extend a unique non-repeat (NR) domain outward away from the bacterial surface to mediate adhesion. So far, NR domains have been determined to bind to sialic acid moieties, keratins, or other NR domains of a similar SRRP. This review summarizes how this important family of bacterial adhesins mediates bacterial attachment to host and bacterial cells, contributes to disease pathogenesis, and might be targeted for pharmacological intervention or used as novel protective vaccine antigens. This review also highlights recent structural findings on the NR domains of these proteins.
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Affiliation(s)
- A Lizcano
- Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, USA
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64
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Blanchette KA, Orihuela CJ. Future perspective on host-pathogen interactions during bacterial biofilm formation within the nasopharynx. Future Microbiol 2012; 7:227-39. [PMID: 22324992 DOI: 10.2217/fmb.11.160] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Nasopharyngeal colonization provides bacteria with a place of residence, a platform for person-to-person transmission and for many opportunistic pathogens it is a prerequisite event towards the development of invasive disease. Therefore, how host factors within the nasopharynx contribute to, inhibit or otherwise shape biofilm formation, the primary mode of existence for colonizing bacteria, and how biofilm bacteria subvert the acute inflammatory response that facilitates clearance, are important topics for future microbiological research. This review proposes the examination of host components as bridging molecules for bacterial interactions during biofilm formation, altered virulence determinant production and cell wall modification as a mechanism for immunoquiescence, and the role of host factors as signals and co-opted mechanisms for bacterial dissemination, together providing an opportunity for disease.
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Affiliation(s)
- Krystle A Blanchette
- The University of Texas Health Science Center at San Antonio, Department of Microbiology & Immunology, 7703 Floyd Curl Drive, MC7758, San Antonio, TX 78229-3900, USA
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Baker HM, Baker EN. A structural perspective on lactoferrin function1This article is part of a Special Issue entitled Lactoferrin and has undergone the Journal's usual peer review process. Biochem Cell Biol 2012; 90:320-8. [PMID: 22292559 DOI: 10.1139/o11-071] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The 3-D structure of human lactoferrin was first solved in atomic detail in 1987. Since that time, a variety of proven and postulated activities have been added to the original annotation of lactoferrin as an iron-binding protein. Structural studies have also expanded to include iron-bound and iron-free (apo) forms, mutants, and the lactoferrins of different species. In this review, we take the current information on both structure and function and show that the 3-D structure provides a useful framework for understanding some activities and also points to productive research directions that could help elucidate other reported functions. Some functions relate to iron binding where the role of lactoferrin is to scavenge and retain iron across a wide pH range. We specifically focus on functions that depend on the surface structure of the molecule, identifying features that may determine the many other protective properties of this multifunctional protein.
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Affiliation(s)
- Heather M. Baker
- School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand
| | - Edward N. Baker
- School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand
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Bensing BA, Yen YT, Seepersaud R, Sullam PM. A Specific interaction between SecA2 and a region of the preprotein adjacent to the signal peptide occurs during transport via the accessory Sec system. J Biol Chem 2012; 287:24438-47. [PMID: 22654116 DOI: 10.1074/jbc.m112.378059] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The accessory Sec systems of streptococci and staphylococci mediate the transport of a family of large, serine-rich glycoproteins to the bacterial cell surface. These systems are comprised of SecA2, SecY2, and three core accessory Sec proteins (Asp1-3). In Streptococcus gordonii, transport of the serine-rich glycoprotein GspB requires both a unique 90-residue N-terminal signal peptide and an adjacent 24-residue segment (the AST domain). We used in vivo site-specific photo-cross-linking to identify proteins that interact with the AST domain during transport. To facilitate this analysis, the entire accessory Sec system of S. gordonii was expressed in Escherichia coli. The determinants of GspB trafficking to the accessory Sec system in E. coli matched those in S. gordonii, establishing the validity of this approach. When the photo-cross-linker was placed within the AST domain, the preprotein was found to cross-link to SecA2. Importantly, no cross-linking to SecA was detected. Cross-linking of the N-terminal end of the AST domain to SecA2 occurred regardless of whether Asp1-3 were present. However, cross-linking to the C-terminal end was dependent on the Asps. The combined results indicate that full engagement of the AST domain by SecA2 is modulated by one or more of the Asps, and suggest that this process is important for initiating transport.
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Affiliation(s)
- Barbara A Bensing
- San Francisco Veterans Affairs Medical Center and the University of California, San Francisco, California 94121, USA
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Garnett JA, Simpson PJ, Taylor J, Benjamin SV, Tagliaferri C, Cota E, Chen YYM, Wu H, Matthews S. Structural insight into the role of Streptococcus parasanguinis Fap1 within oral biofilm formation. Biochem Biophys Res Commun 2012; 417:421-6. [PMID: 22166217 PMCID: PMC3518267 DOI: 10.1016/j.bbrc.2011.11.131] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Accepted: 11/28/2011] [Indexed: 12/22/2022]
Abstract
The fimbriae-associated protein 1 (Fap1) is a major adhesin of Streptococcus parasanguinis, a primary colonizer of the oral cavity that plays an important role in the formation of dental plaque. Fap1 is an extracellular adhesive surface fibre belonging to the serine-rich repeat protein (SRRP) family, which plays a central role in the pathogenesis of streptococci and staphylococci. The N-terminal adhesive region of Fap1 (Fap1-NR) is composed of two domains (Fap1-NR(α) and Fap1-NR(β)) and is projected away from the bacterial surface via the extensive serine-rich repeat region, for adhesion to the salivary pellicle. The adhesive properties of Fap1 are modulated through a pH switch in which a reduction in pH results in a rearrangement between the Fap1-NR(α) and Fap1-NR(β) domains, which assists in the survival of S. parasanguinis in acidic environments. We have solved the structure of Fap1-NR(α) at pH 5.0 at 3.0Ǻ resolution and reveal how subtle rearrangements of the 3-helix bundle combined with a change in electrostatic potential mediates 'opening' and activation of the adhesive region. Further, we show that pH-dependent changes are critical for biofilm formation and present an atomic model for the inter-Fap1-NR interactions which have been assigned an important role in the biofilm formation.
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Affiliation(s)
- James A. Garnett
- Department of Biological Sciences, Centre for Structural Biology, Imperial College London, South Kensington, London SW7 2AZ, UK
| | - Peter J. Simpson
- Department of Biological Sciences, Centre for Structural Biology, Imperial College London, South Kensington, London SW7 2AZ, UK
| | - Jonathan Taylor
- Department of Biological Sciences, Centre for Structural Biology, Imperial College London, South Kensington, London SW7 2AZ, UK
| | - Stefi V. Benjamin
- Department of Biological Sciences, Centre for Structural Biology, Imperial College London, South Kensington, London SW7 2AZ, UK
| | - Camille Tagliaferri
- Department of Biological Sciences, Centre for Structural Biology, Imperial College London, South Kensington, London SW7 2AZ, UK
| | - Ernesto Cota
- Department of Biological Sciences, Centre for Structural Biology, Imperial College London, South Kensington, London SW7 2AZ, UK
| | - Yi-Ywan M. Chen
- Department of Microbiology & Immunology, and Research Center for Pathogenic Bacteria, Chang Gung University, Tao-Yuan, Taiwan
| | - Hui Wu
- Department of Pediatric Dentistry, University of Alabama at Birmingham, School of Dentistry, Birmingham, AL 35294
| | - Stephen Matthews
- Department of Biological Sciences, Centre for Structural Biology, Imperial College London, South Kensington, London SW7 2AZ, UK
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