Evidence for the alpha-helicity of class II MHC molecular binding sites for the superantigen, staphylococcal enterotoxin A. |
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| Authors: | J K Russell M A Jarpe H M Johnson |
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| Institution: | Department of Microbiology and Cell Science, University of Florida, Gainesville 32611. |
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| Abstract: | Circular dichroism (CD) spectra of class II MHC peptides revealed the alpha-helical conformation of superantigen-binding peptides I-A beta b(60-90), I-A beta b(65-85), and I-A alpha b(51-80), but not the nonbinding peptide I-A beta b(80-100). These CD spectra provide biophysical evidence for the alpha-helicity of class II MHC molecular binding sites for the superantigen, staphylococcal enterotoxin A (SEA). Alanine-substituted analogs of the SEA binding-site peptide, I-A beta b(65-85), were used to implicate beta-chain residues 72 and 80 in class II MHC-SEA binding. The data support SEA binding away from the class II antigen binding cleft along the faces of the alpha-helices. |
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