scholarly journals The Factor H Binding Protein ofNeisseria meningitidisInteracts with Xenosiderophores in Vitro

Biochemistry ◽  
2012 ◽  
Vol 51 (46) ◽  
pp. 9384-9393 ◽  
Author(s):  
Daniele Veggi ◽  
Maria A. Gentile ◽  
Francesca Cantini ◽  
Paola Lo Surdo ◽  
Vincenzo Nardi-Dei ◽  
...  
Keyword(s):  
Binding Protein ◽  
Factor H

scholarly journals Complement Factor H Is a Serum-binding Protein for Adrenomedullin, and the Resulting Complex Modulates the Bioactivities of Both Partners

2000 ◽  
Vol 276 (15) ◽  
pp. 12292-12300 ◽  
Author(s):  
Rubén Pı́o ◽  
Alfredo Martı́nez ◽  
Edward J. Unsworth ◽  
Jeffrey A. Kowalak ◽  
José A. Bengoechea ◽  
...  
Keyword(s):  
Binding Protein ◽  
Polyacrylamide Gel Electrophoresis ◽  
Cancer Cell Line ◽  
Factor H ◽  
Complement Factor H ◽  
Regulatory Function ◽  
Complement Factor ◽  
Routine Procedure ◽  
Serum Binding Protein

Adrenomedullin (AM) is an important regulatory peptide involved in both physiological and pathological states. We have previously demonstrated the existence of a specific AM-binding protein (AMBP-1) in human plasma. In the present study, we developed a nonradioactive ligand blotting assay, which, together with high pressure liquid chromatography/SDS-polyacrylamide gel electrophoresis purification techniques, allowed us to isolate AMBP-1 to homogeneity. The purified protein was identified as human complement factor H. We show that AM/factor H interaction interferes with the established methodology for quantification of circulating AM. Our data suggest that this routine procedure does not take into account the AM bound to its binding protein. In addition, we show that factor H affects AMin vitrofunctions. It enhances AM-mediated induction of cAMP in fibroblasts, augments the AM-mediated growth of a cancer cell line, and suppresses the bactericidal capability of AM onEscherichia coli. Reciprocally, AM influences the complement regulatory function of factor H by enhancing the cleavage of C3b via factor I. In summary, we report on a potentially new regulatory mechanism of AM biology, the influence of factor H on radioimmunoassay quantification of AM, and the possible involvement of AM as a regulator of the complement cascade.

scholarly journals Relapsing Fever Spirochetes Borrelia recurrentis and B. duttonii Acquire Complement Regulators C4b-Binding Protein and Factor H

2006 ◽  
Vol 74 (7) ◽  
pp. 4157-4163 ◽  
Author(s):  
T. Meri ◽  
S. J. Cutler ◽  
A. M. Blom ◽  
S. Meri ◽  
T. S. Jokiranta
Keyword(s):  
Binding Protein ◽  
Protein A ◽  
Sensu Stricto ◽  
Factor H ◽  
Complement Pathway ◽  
Relapsing Fever ◽  
Borrelia Recurrentis ◽  
First Report ◽  
Complement Regulators

ABSTRACT Relapsing fever is a rapidly progressive and severe septic disease caused by certain Borrelia spirochetes. The disease is divided into two forms, i.e., epidemic relapsing fever, caused by Borrelia recurrentis and transmitted by lice, and the endemic form, caused by several Borrelia species, such as B. duttonii, and transmitted by soft-bodied ticks. The spirochetes enter the bloodstream by the vector bite and live persistently in plasma even after the development of specific antibodies. This leads to fever relapses and high mortality and clearly indicates that the Borrelia organisms utilize effective immune evasion strategies. In this study, we show that the epidemic relapsing fever pathogen B. recurrentis and an endemic relapsing fever pathogen, B. duttonii, are serum resistant, i.e., resistant to complement in vitro. They acquire the host alternative complement pathway regulator factor H on their surfaces in a similar way to that of the less serum-resistant Lyme disease pathogen, B. burgdorferi sensu stricto. More importantly, the relapsing fever spirochetes specifically bind host C4b-binding protein, a major regulator of the antibody-mediated classical complement pathway. Both complement regulators retained their functional activities when bound to the surfaces of the spirochetes. In conclusion, this is the first report of complement evasion by Borrelia recurrentis and B. duttonii and the first report showing capture of C4b-binding protein by spirochetes.

scholarly journals The Borrelia hermsii Factor H Binding Protein FhbA Is Not Required for Infectivity in Mice or for Resistance to Human ComplementIn Vitro

2014 ◽  
Vol 82 (8) ◽  
pp. 3324-3332 ◽  
Author(s):  
Lindy M. Fine ◽  
Daniel P. Miller ◽  
Katherine L. Mallory ◽  
Brittney K. Tegels ◽  
Christopher G. Earnhart ◽  
...  
Keyword(s):  
Genetic Manipulation ◽  
Binding Protein ◽  
Factor H ◽  
Negative Regulator ◽  
Human Complement ◽  
Relapsing Fever ◽  
Borrelia Hermsii ◽  
Content Type

ABSTRACTThe primary causative agent of tick-borne relapsing fever in North America isBorrelia hermsii. It has been hypothesized thatB. hermsiievades complement-mediated destruction by binding factor H (FH), a host-derived negative regulator of complement.In vitro,B. hermsiiproduces a single FH binding protein designated FhbA (FH binding protein A). The properties and ligand binding activity of FhbA suggest that it plays multiple roles in pathogenesis. It binds plasminogen and has been identified as a significant target of a B1b B cell-mediated IgM response in mice. FhbA has also been explored as a potential diagnostic antigen forB. hermsiiinfection in humans. The ability to test the hypothesis that FhbA is a critical virulence factorin vivohas been hampered by the lack of well-developed systems for the genetic manipulation of the relapsing fever spirochetes. In this report, we have successfully generated aB. hermsiifhbAdeletion mutant (theB. hermsiiYORΔfhbAstrain) through allelic exchange mutagenesis. Deletion offhbAabolished FH binding by the YORΔfhbAstrain and eliminated cleavage of C3b on the cell surface. However, the YORΔfhbAstrain remained infectious in mice and retained resistance to killingin vitroby human complement. Collectively, these results indicate thatB. hermsiiemploys an FhbA/FH-independent mechanism of complement evasion that allows for resistance to killing by human complement and persistence in mice.

scholarly journals Loa loa Microfilariae Evade Complement Attack In Vivo by Acquiring Regulatory Proteins from Host Plasma

2009 ◽  
Vol 77 (9) ◽  
pp. 3886-3893 ◽  
Author(s):  
Karita Haapasalo ◽  
Taru Meri ◽  
T. Sakari Jokiranta
Keyword(s):  
Complement Activation ◽  
Blood Circulation ◽  
Binding Protein ◽  
Factor H ◽  
Loa Loa ◽  
Continuous Contact ◽  
Subcutaneous Tissues ◽  
Complement Regulators

ABSTRACT Loa loa is a filarial nematode that infects humans. The adults live in subcutaneous tissues and produce microfilariae that live for several weeks in the blood circulation in order to be transmitted to another person via blood meals of a dipterian vector. As microfilariae live in continuous contact with plasma, it is obvious that they evade the complement system. We studied markers of complement activation and signs of complement regulation on Loa loa microfilariae in vivo. The microfilariae were isolated from anticoagulated blood samples of a Loa loa-infected Caucasian patient. C1q and some mannose-binding lectin but only a limited amount of C3b or C4b fragments and practically no C5 or C5b-9 were present on the microfilariae. The covalently microfilaria-bound C3 and C4 depositions were mainly inactive iC3b, C3c, and iC4b fragments indicating that microfilariae had regulated complement activation in vivo. Also, in vitro deposition of C3b onto the microfilariae upon serum exposure was limited. The patient-isolated microfilariae were found to carry the host complement regulators factor H and C4b-binding protein on the outermost layer, so called sheath. The microfilaria-bound factor H was functionally active. Binding of the complement regulators to the microfilariae was confirmed in vitro using 125I-labeled factor H and C4b-binding protein. In conclusion, our study shows that Loa loa microfilariae block complement activation and acquire the host complement regulators factor H and C4b-binding protein in blood circulation. This is the first time that binding of complement regulators onto nonviral pathogens has been demonstrated to occur in humans in vivo.

scholarly journals Neisseria meningitidis factor H-binding protein bound to monoclonal antibody JAR5: implications for antibody synergy

2016 ◽  
Vol 473 (24) ◽  
pp. 4699-4713 ◽  
Author(s):  
Enrico Malito ◽  
Paola Lo Surdo ◽  
Daniele Veggi ◽  
Laura Santini ◽  
Heather Stefek ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Monoclonal Antibodies ◽  
Neisseria Meningitidis ◽  
Binding Protein ◽  
Factor H ◽  
Structural Basis ◽  
Fab Fragment ◽  
Bacterial Killing ◽  
Fragment Antigen Binding

Factor H-binding protein (fHbp) is an important antigen of Neisseria meningitidis that is capable of eliciting a robust protective immune response in humans. Previous studies on the interactions of fHbp with antibodies revealed that some anti-fHbp monoclonal antibodies that are unable to trigger complement-mediated bacterial killing in vitro are highly co-operative and become bactericidal if used in combination. Several factors have been shown to influence such co-operativity, including IgG subclass and antigen density. To investigate the structural basis of the anti-fHbp antibody synergy, we determined the crystal structure of the complex between fHbp and the Fab (fragment antigen-binding) fragment of JAR5, a specific anti-fHbp murine monoclonal antibody known to be highly co-operative with other monoclonal antibodies. We show that JAR5 is highly synergic with monoclonal antibody (mAb) 12C1, whose structure in complex with fHbp has been previously solved. Structural analyses of the epitopes recognized by JAR5 and 12C1, and computational modeling of full-length IgG mAbs of JAR5 and 12C1 bound to the same fHbp molecule, provide insights into the spatial orientation of Fc (fragment crystallizable) regions and into the possible implications for the susceptibility of meningococci to complement-mediated killing.

scholarly journals Expression of Factor H Binding Protein of Meningococcus Responds to Oxygen Limitation through a Dedicated FNR-Regulated Promoter

2009 ◽  
Vol 192 (3) ◽  
pp. 691-701 ◽  
Author(s):  
Francesca Oriente ◽  
Vincenzo Scarlato ◽  
Isabel Delany
Keyword(s):  
Molecular Mechanisms ◽  
Binding Protein ◽  
Alternative Pathway ◽  
Oxygen Limitation ◽  
Factor H ◽  
Dependent Manner ◽  
Complement Alternative Pathway ◽  
Upstream Gene ◽  
Binding Factor

ABSTRACT Factor H binding protein (fHBP) is a surface-exposed lipoprotein in Neisseria meningitidis, which is a component of several investigational vaccines against serogroup B meningococcus (MenB) currently in development. fHBP enables the bacterium to evade complement-mediated killing by binding factor H, a key downregulator of the complement alternative pathway, and, in addition, fHBP is important for meningococcal survival in the presence of the antimicrobial peptide LL-37. In this study, we investigate the molecular mechanisms involved in transcription and regulation of the fHBP-encoding gene, fhbp. We show that the fHBP protein is expressed from two independent transcripts: one bicistronic transcript that includes the upstream gene and a second shorter monocistronic transcript from its own dedicated promoter, P fhbp . Transcription from the promoter P fhbp responds to oxygen limitation in an FNR-dependent manner, and, accordingly, the FNR protein binds to a P fhbp probe in vitro. Furthermore, expression in meningococci of a constitutively active FNR mutant results in the overexpression of the fHBP protein. Finally, the analysis of fHBP regulation was extended to a panel of strains expressing different fHBP allelic variants at different levels, and we demonstrate that FNR is involved in the regulation of this antigen in all but one of the strains tested. Our data suggest that oxygen limitation may play an important role in inducing the expression of fHBP from a dedicated FNR-regulated promoter. This implies a role for this protein in microenvironments lacking oxygen, for instance in the submucosa or intracellularly, in addition to its demonstrated role in serum resistance in the blood.

scholarly journals PenA, a penicillin-binding protein-type thioesterase specialized for small peptide cyclization

2021 ◽  
Author(s):  
Kenichi Matsuda ◽  
Kei Fujita ◽  
Toshiyuki Wakimoto
Keyword(s):  
Enzymatic Activity ◽  
Computational Model ◽  
Binding Protein ◽  
Penicillin Binding Protein ◽  
Small Peptide ◽  
Peptide Cyclization ◽  
Chain Lengths ◽  
Non Ribosomal Peptides

Abstract Penicillin binding protein-type thioesterases (PBP-type TEs) are a recently identified group of peptide cyclases that catalyze head-to-tail macrolactamization of non-ribosomal peptides. PenA, a new member of this group, is involved in the biosyntheses of cyclic pentapeptides. In this study, we demonstrated the enzymatic activity of PenA in vitro, and analyzed its substrate scope with a series of synthetic substrates. A comparison of the reaction profiles between PenA and SurE, a representative PBP-type TE, showed that PenA is more specialized for small peptide cyclization. A computational model provided a possible structural rationale for the altered specificity for substrate chain lengths.

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