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Variable region structure and staphylococcal protein A binding specificity of a mouse monoclonal IgM
G C Feijó1, J Sabbaga, C R Carneiro
1Department of Cell Biology, University of Brasília, Brazil.
Abstract:
Staphylococcal protein A is a cell wall-attached polypeptide that acts as a B-lymphocyte superantigen. This activation correlates with specific VH gene segment usage in the B-cell receptor. B-cell receptor assembled from members of the VH3 family in humans, or S107 family in mice, has an intrinsic affinity for protein A. Human VH3-derived antibodies bind to domain D of protein A. We have characterized a mouse IgM monoclonal antibody that binds protein A. The sequencing of the variable region suggests an almost germline-encoded VH derived from S107 family and a V kappa 8-derived VL. The binding specificity of the monoclonal antibody was tested with various recombinant constructions derived from protein A. We show that, unlike human VH3-derived antibody, mouse S107-derived immunoglobulin binds to the B domain of the bacterial superantigen.