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 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 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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