Site of nonrestrictive binding of SEA to class II MHC antigens.
We have used the synthetic peptide approach to show that the N-terminal 45-amino acids of staphylococcal enterotoxin A (SEA), SEA(1-45), constitute an important part of its binding site on class II major histocompatibility complex (MHC) molecules. SEA(1-45) and to a lesser extent SEA(1-27) were able to displace SEA from HLA-DR on Raji cells as assessed by flow cytometry and to compete with radiolabeled SEA for interaction with HLA-DR in a direct binding assay. Specific binding of SEA to Ia on murine A-20 cells could be inhibited by the same peptides [i.e. SEA(1-45) greater than SEA(1-27)] that blocked binding to HLA-DR. Therefore, different class II MHC molecules associate with the same functional site on SEA. Further, an ELISA system was used to demonstrate that SEA(1-45) is able to directly bind to a mouse synthetic I-A beta b peptide, I-A beta b (65-85), which contains a binding site of the class II MHC molecule involved in SEA presentation to T cells. Thus, we have localized a site on SEA that is involved in selective surface association with class II MHC antigens and identified the region on the class II MHC antigen to which that site binds.
Pontzer
C H
CH
Department of Microbiology and Cell Science, University of Florida, Gainesville.
Russell
J K
JK
Jarpe
M A
MA
Johnson
H M
HM
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D004768:Enterotoxins / Q000378:metabolism*; D006684:HLA-DR Antigens / Q000378:metabolism*; D051379:Mice; D010446:Peptide Fragments / Q000378:metabolism; D013211:Staphylococcus aureus / Q000472:pathogenicity*
D004768:Enterotoxins; D006684:HLA-DR Antigens; D010446:Peptide Fragments; C026066:enterotoxin A, Staphylococcal