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Monoclonal antibody analysis of diphtheria toxin—II. Inhibition of ADP-ribosyltransferase activity

Authors
Journal
Molecular Immunology
0161-5890
Publisher
Elsevier
Publication Date
Volume
21
Issue
9
Identifiers
DOI: 10.1016/0161-5890(84)90166-4
Disciplines
  • Biology

Abstract

Abstract Monoclonal antibodies directed against the enzymatically active A-fragment of diphtheria toxin were used to investigate further the structure-function relationships within fragment A. Of 16 such antibodies, all but two were directed against epitopes located within the carboxy-terminal 30–40 amino acids of fragment A. Interestingly, the antibodies recognize several epitopes in this small region and varied considerably in their effects on toxin functions. With regard to their effects on the enzymatic activity of fragment A, three types of antibodies were found: (1) antibodies which bind fragment A but fail to inhibit its ADP-ribosyltransferase activity, (2) antibodies which completely inhibit enzyme activity, and (3) antibodies which interact with fragment A to yield antigen-antibody complexes of diminished activity. The results are consistent with location of the catalytic center of fragment A within its carboxy-terminal ca 4000 dalton region.

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