A small domain (6.5 kDa) of bacterial protein G inhibits C3 covalent binding to the Fc region of IgG immune complexes.

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dc.contributor.authorMuñoz, Esther
dc.contributor.authorVidarte, Luis
dc.contributor.authorPastor Vargas, Carlos
dc.contributor.authorCasado, Maria Teresa
dc.contributor.authorVivanco Martínez, Fernando
dc.date.accessioned2024-01-15T10:36:57Z
dc.date.available2024-01-15T10:36:57Z
dc.date.issued1998
dc.description.abstractAttachment of the complement component C3 to antigen-antibody (Ag-Ab) complexes (immune complexes, IC) is the key molecular event responsible for the elimination of many Ag in the form of Ag-Ab-C3b. The CH1 domain and the Fc region of the Ab, which have previously been involved in the binding of C3b, are also the targets of several bacterial IgG-binding proteins, particularly proteins G and A. Here we describe the ability of a small recombinant protein G domain (B2; 6.5 kDa) to inhibit the covalent binding of C3b to the Fc portion of IgG without affecting the binding to the Fab part. Protein G (B2 domain) produced a remarkable inhibition of covalent binding of C3b to IC formed with rabbit IgG, but none with the F(ab')2 fragment, indicating that B2 interferes with the C3b binding to the Fc region. A weak inhibition was observed with IC formed with mouse IgG2b which preferentially binds B2 domain on the CH1 domain of the Fab. To confirm these data, recombinant single-chain Ab devoid of CH1 domains (scAb), and including the rabbit or human Fc portion (hinge-CH2-CH3), were produced and used to form IC. Protein G-B2 domain inhibited C3b binding to IC formed with scAb of either human or rabbit constant regions, supporting the view of a specific blockade of C3b binding to the Fc region. A similar inhibition of C3b binding was observed using protein A instead of protein G B2 domain and the same set of IC. On the CH1 domain, C3b and B2 bind on opposite faces, and therefore do not interfere with each other in their binding. However, B2 domain bound to the inter-CH2-CH3 region impedes the C3b binding to the Fc. This inhibition clarifies the specificity of C3b for the different regions of IgG and explains how bacterial IgG-binding proteins provide the bacteria with a mechanism of evasion from the opsonizing action of complement and contribute to the virulence. This could be a general mechanism of escape because protein G binds the majority of mammalian Ig.
dc.description.departmentDepto. de Bioquímica y Biología Molecular
dc.description.facultyFac. de Ciencias Químicas
dc.description.refereedTRUE
dc.description.sponsorshipMinisterio de Educación (España)
dc.description.sponsorshipComunidad de Madrid
dc.description.statuspub
dc.identifier.citationMuñoz E, Vidarte L, Pastor C, Casado M, Vivanco F. A small domain (6.5 kDa) of bacterial protein G inhibits C3 covalent binding to the Fc region of IgG immune complexes. Eur J Immunol. 1998 Aug;28(8):2591-7. doi: 10.1002/(SICI)1521-4141(199808)28:08<2591::AID-IMMU2591>3.0.CO;2-P. PMID: 9710236.
dc.identifier.doi10.1002/(SICI)1521-4141(199808)28:08<2591::AID-IMMU2591>3.0.CO;2-P
dc.identifier.issn1521-4141
dc.identifier.officialurlhttps://doi.org/10.1002/(SICI)1521-4141(199808)28:08%3C2591::AID-IMMU2591%3E3.0.CO;2-P
dc.identifier.urihttps://hdl.handle.net/20.500.14352/93008
dc.issue.number8
dc.journal.titleEuropean Journal of Immunology
dc.language.isoeng
dc.page.final2597
dc.page.initial2591
dc.publisherWiley
dc.relation.projectIDPM95-0046
dc.relation.projectID94/AE0282
dc.rightsAttribution-NonCommercial-NoDerivatives 4.0 Internationalen
dc.rights.accessRightsopen access
dc.rights.urihttp://creativecommons.org/licenses/by-nc-nd/4.0/
dc.subject.cdu612.017
dc.subject.keywordC3
dc.subject.keywordProtein G
dc.subject.keywordFc
dc.subject.keywordBacterium
dc.subject.keywordAntigen-antibody complex
dc.subject.ucmInmunología
dc.subject.unesco2412 Inmunología
dc.titleA small domain (6.5 kDa) of bacterial protein G inhibits C3 covalent binding to the Fc region of IgG immune complexes.
dc.typejournal article
dc.type.hasVersionVoR
dc.volume.number28
dspace.entity.typePublication
relation.isAuthorOfPublication25af78c7-0077-4891-a14e-bcd8e51fe408
relation.isAuthorOfPublication6f3e7679-cbc7-4f23-8355-2de0876d46ad
relation.isAuthorOfPublication.latestForDiscovery25af78c7-0077-4891-a14e-bcd8e51fe408
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