scholarly journals Perturbation of the antigen-binding site and staphylococcal Protein A-binding site of IgG before significant changes in global conformation during denaturation: an equilibrium study

1997 ◽  
Vol 325 (3) ◽  
pp. 707-710 ◽  
Author(s):  
Xi-De WANG ◽  
Jie LUO ◽  
Zhen-Quan GUO ◽  
Jun-Mei ZHOU ◽  
Chen-Lu TSOU
Keyword(s):  
Ligand Binding ◽  
Binding Site ◽  
Conformational Changes ◽  
Active Sites ◽  
Protein A ◽  
Staphylococcal Protein A ◽  
Antigen Binding Site ◽  
Antibody Molecule ◽  
Staphylococcal Protein ◽  
Equilibrium Study

Although conformational perturbation of the active sites of many enzymes has been reported to precede global molecular conformational changes [Tsou (1993) Science 262, 380–381], little effort has been made to compare the susceptibility of the ligand-binding site of proteins and the protein molecules as a whole to perturbation by denaturants. Immunoglobulin is chosen in this study to address this problem. It is found that the variable and constant regions (Fv and Fc) of a monoclonal antibody of an IgG subclass against adenylate kinase lose their abilities to bind antigen and staphylococcal Protein A after treatment with guanidinium chloride concentrations considerably lower than those required to change the global conformation of the antibody as a whole, as detected by fluorescence and second-derivative UV absorption spectroscopy. These results indicate that both ligand-binding sites of the antibody concerned are more fragile than the molecule as a whole and that the Fv and Fc regions of the antibody molecule unfold sequentially during denaturation.

scholarly journals Diversity of Functionally Distinct Clonal Sets of Human Conventional Memory B Cells That Bind Staphylococcal Protein A

2021 ◽  
Vol 12 ◽  
Author(s):  
Emily E. Radke ◽  
Zhi Li ◽  
David N. Hernandez ◽  
Hanane El Bannoudi ◽  
Sergei L. Kosakovsky Pond ◽  
...  
Keyword(s):  
Immune System ◽  
B Cells ◽  
B Cell ◽  
Binding Site ◽  
Protein A ◽  
Memory B Cells ◽  
Host Immune System ◽  
Staphylococcal Protein A ◽  
Staphylococcal Protein ◽  
Circulating Antibodies

Staphylococcus aureus, a common cause of serious and often fatal infections, is well-armed with secreted factors that disarm host immune defenses. Highly expressed in vivo during infection, Staphylococcal protein A (SpA) is reported to also contribute to nasal colonization that can be a prelude to invasive infection. Co-evolution with the host immune system has provided SpA with an Fc-antibody binding site, and a Fab-binding site responsible for non-immune superantigen interactions via germline-encoded surfaces expressed on many human BCRs. We wondered whether the recurrent exposures to S. aureus commonly experienced by adults, result in the accumulation of memory B-cell responses to other determinants on SpA. We therefore isolated SpA-specific class-switched memory B cells, and characterized their encoding VH : VL antibody genes. In SpA-reactive memory B cells, we confirmed a striking bias in usage for VH genes, which retain the surface that mediates the SpA-superantigen interaction. We postulate these interactions reflect co-evolution of the host immune system and SpA, which during infection results in immune recruitment of an extraordinarily high prevalence of B cells in the repertoire that subverts the augmentation of protective defenses. Herein, we provide the first evidence that human memory responses are supplemented by B-cell clones, and circulating-antibodies, that bind to SpA determinants independent of the non-immune Fc- and Fab-binding sites. In parallel, we demonstrate that healthy individuals, and patients recovering from S. aureus infection, both have circulating antibodies with these conventional binding specificities. These findings rationalize the potential utility of incorporating specially engineered SpA proteins into a protective vaccine.

scholarly journals IgG rheumatoid factors and staphylococcal protein A bind to a common molecular site on IgG.

1985 ◽  
Vol 162 (6) ◽  
pp. 1811-1824 ◽  
Author(s):  
F A Nardella ◽  
D C Teller ◽  
C V Barber ◽  
M Mannik
Keyword(s):  
Rheumatoid Arthritis ◽  
Amino Acid ◽  
Binding Site ◽  
Antigenic Determinant ◽  
Protein A ◽  
Side Chains ◽  
Staphylococcal Protein A ◽  
Rheumatoid Factors ◽  
Ph Titration ◽  
Staphylococcal Protein

The antigenic determinant on the Fc region of human IgG for two IgG rheumatoid factors (IgG-RF) from patients with rheumatoid arthritis were investigated in detail. The RF did not interact with IgG fragments that contained the C gamma 2 or C gamma 3 region alone, but required the presence of both regions for binding. The RF binding to solid-phase IgG were poorly inhibited by the IgG3 subclass and strongly inhibited by staphylococcal protein A (SPA) (42 kD), and fragment D of SPA (7 kD), indicating that the binding site is most likely the same as the Ga antigenic determinant described for IgM-RF, and is in the same location as the site on IgG that binds SPA. pH titration studies of the RF binding to IgG indicated the involvement of histidine and lysine or tyrosine side chains. Chemical modification studies showed the histidines were involved on the Fc side of the interactions, and tyrosines were involved on both the antigenic and antibody sides of the interactions. Lysines were not involved. The above information, and the knowledge of the number and position in space of the amino acid residues involved in the C gamma 2-C gamma 3 interface region of IgG, the binding site for SPA, and the amino acid substitutions in IgG3 that account for its inability to bind protein A, allowed the identification of the site on IgG that bind IgG-RF. This binding site involves some of the same amino acid side chains, His 435, Tyr 436, and one or both His 433 and 310, and is in the same location as the site that binds SPA. The same site is likely to be a common antigenic determinant for other RF. Furthermore, the described molecular mimicry suggests a biological relationship between bacterial Fc-binding proteins and the production of RF in rheumatoid arthritis.

scholarly journals The structural basis of germline-encoded VH3 immunoglobulin binding to staphylococcal protein A.

1993 ◽  
Vol 178 (1) ◽  
pp. 331-336 ◽  
Author(s):  
J L Hillson ◽  
N S Karr ◽  
I R Oppliger ◽  
M Mannik ◽  
E H Sasso
Keyword(s):  
T Cell ◽  
Present Report ◽  
Protein A ◽  
Structural Basis ◽  
Staphylococcal Protein A ◽  
Antigen Binding Site ◽  
Staphylococcal Protein ◽  
Germline Genes ◽  
Immunoglobulin Binding ◽  
Framework Region

The ability of human VH3 immunoglobulins (Ig) to bind to staphylococcal protein A (SPA) via their Fab region is analogous to the binding of bacterial superantigens to T cell receptors. The present report establishes the structural basis for the interaction of SPA and VH3 Ig. We have studied a panel of 27 human monoclonal IgM that were derived from fetal B lymphocytes. As such, these IgM were expected to be encoded by unmutated germline genes. Binding to SPA in ELISA occurred with 15 of 15 VH3 IgM, but none of 12 IgM from the VH1, VH4, VH5, or VH6 families. The VH sequences of the 27 IgM were derived from 20 distinct VH elements, including 11 from the VH3 family. Use of D, JH, and CL genes was similar among VH3 and non-VH3 IgM. A comparison of the corresponding VH protein sequences, and those of previously studied IgM, identified a probable site for SPA binding that includes VH3 residues in framework region 3 (FR3), and perhaps FR1 and 3' complementary determining region 2. The results thus demonstrate that among human IgM, specificity for SPA is encoded by at least 11 different VH3 germline genes. Furthermore, like the T cell superantigens, SPA likely binds to residues in the VH framework region, outside the classical antigen-binding site of the hypervariable loops.

scholarly journals Quantification of platelet-bound IgG by 125I-Staphylococcal protein A in immune thrombocytopenic purpura and other thrombocytopenic disorders

Blood ◽  
1984 ◽  
Vol 63 (1) ◽  
pp. 154-161 ◽  
Author(s):  
GM Shaw ◽  
J Axelson ◽  
JG Maglott ◽  
AF LoBuglio
Keyword(s):  
Immune Thrombocytopenic Purpura ◽  
Protein A ◽  
Normal Subjects ◽  
Unknown Etiology ◽  
Staphylococcal Protein A ◽  
Thrombocytopenic Purpura ◽  
Clinical Criteria ◽  
Staphylococcal Protein ◽  
Wide Range ◽  
Immune Hemolytic Anemia

Abstract In this report we describe the use of an 125I-Staphylococcal protein A (SPA) assay to measure platelet-bound IgG in the evaluation of 62 thrombocytopenic patients. Platelets from 150 normal subjects were found to bind 146 +/- 112 molecules of SPA per platelet (mean +/- 2 SD). Nineteen of 20 patients with untreated immune thrombocytopenia had platelet IgG values above this range, with 15 of 20 having values above 1,000 molecules of SPA per platelet. Patients with immune thrombocytopenic purpura by clinical criteria, but who had failed conventional therapy (corticosteroids or splenectomy), had a wide range of platelet IgG levels: 4 of 20 had normal values, 6 of 20 had minimally elevated levels in the range seen with nonimmune thrombocytopenia, and 10 of 20 had much higher values. Fifteen patients with thrombocytopenia of apparent nonimmune origin and 7 others with chronic stable thrombocytopenia of unknown etiology were found to have platelet IgG levels within or only slightly above the normal range. Because of its simplicity, accuracy, and clinical correlation, the 125I- SPA assay provides an important new approach for studying platelet IgG in thrombocytopenic states. The data obtained with this technique are similar to those found in immune hemolytic anemia and suggest that the platelet-bound IgG so measured has pathophysiologic relevance in immune thrombocytopenic purpura.

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