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Cryptic and regulatory epitopes in CD13/aminopeptidase N
Y Xu1, D Wellner, D A Scheinberg
1Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
Experimental Hematology
|June 1, 1997
Summary
CD13/Aminopeptidase N (APN) undergoes conformational changes affecting its epitopes upon substrate or inhibitor binding. These intramolecular changes regulate enzyme function without altering its dimeric structure.
Area of Science:
- Biochemistry
- Cell Biology
- Enzymology
Background:
- CD13/Aminopeptidase N (APN) is a cell surface enzyme with roles in peptide signal regulation, viral binding, and tumor invasion.
- Understanding CD13/APN's functional mechanisms is crucial for its therapeutic targeting.
Purpose of the Study:
- To investigate the functional aspects of CD13/Aminopeptidase N (APN) using specific monoclonal antibodies and enzyme substrates/inhibitors.
- To elucidate the structural dynamics and epitope accessibility of CD13/APN in response to ligand binding.
Main Methods:
- Utilized monoclonal antibodies (F23, MY7) targeting distinct CD13/APN epitopes.
- Employed flow cytometry and radiobinding assays with Scatchard analysis for epitope quantitation.
- Applied cross-linking techniques and gel electrophoresis to determine the oligomeric state of CD13/APN.
Main Results:
- Antibodies F23 and MY7 differentially inhibited CD13/APN activity and substrate binding.
- Ligand binding induced conformational changes, altering the accessibility of MY7 epitopes.
- CD13/APN exists as a dimer, and these conformational shifts are intramolecular, not affecting protomer association.
Conclusions:
- Cryptic epitopes on CD13/APN contribute to varied antibody effects on enzyme activity.
- Substrate binding involves the zinc domain, affecting both F23 and MY7 epitopes, while inhibitors primarily affect F23 epitopes.
- CD13/APN regulation involves intramolecular conformational changes within a stable dimeric structure.