Chemical and immunochemical studies on the receptor binding domain of cholera toxin B subunit.
The contributions of various amino acids to the structure and function of cholera toxin B subunit were assessed with quantifiable, chemically conservative, reversible derivatizations, and sensitive assays of activity. A panel of monoclonal antibodies was employed to monitor the conformational integrity of modified protein and help distinguish the direct from indirect effects of chemical derivatization. We describe a novel monoclonal antibody, which competes with the receptor GM1 for binding to cholera toxin B subunit, and use this reagent to help identify critically located residues. Our data support the hypothesis that tryptophan participates directly in binding GM1. In addition, we propose a dual role for lysine: first, these basic residues maintain an electrostatic attraction vital to receptor recognition; second, at least 1 lysine resides near the receptor binding domain and may interact with GM1. The influence of arginyl and tyrosyl residues upon activity is re-examined. Finally, we present data which suggest, in variance with previous studies, that the intramolecular disulfide bond is vital to the structure and function of cholera toxin B subunit.
D S
DS
Ludwig
R K
RK
Holmes
G K
GK
Schoolnik
D000911:Antibodies, Monoclonal; D001120:Arginine; D001667:Binding, Competitive; D055598:Chemical Phenomena; D002621:Chemistry; D002772:Cholera Toxin / Q000276:immunology / Q000378:metabolism*; D004220:Disulfides; D000939:Epitopes / Q000276:immunology; D005677:G(M1) Ganglioside / Q000378:metabolism*; D007158:Immunologic Techniques; D008239:Lysine; D009844:Oligosaccharides / Q000378:metabolism; D011487:Protein Conformation; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014364:Tryptophan; D014443:Tyrosine
D000911:Antibodies, Monoclonal; D004220:Disulfides; D000939:Epitopes; D009844:Oligosaccharides; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; C023552:choleragen receptor; D005677:G(M1) Ganglioside; D014443:Tyrosine; D014364:Tryptophan; D002772:Cholera Toxin; D001120:Arginine; D008239:Lysine