Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
Board

Angiotensin II (AngII: Asp-Arg-Val-Tyr-Ile-His-Pro-Phe) is an octapeptide hormone playing an important role in the regulation of blood pressure. AngII activates two different types of receptors (AT1 and AT2) that belong to the G-protein-coupled receptors superfamily. We are using a strategy to identify the contact points between AngII and its receptors. With radioactive photosensitive analogs of AngII (where any amino acid residue of AngII can be substituted for p-benzoylphenylalanine (Bpa) AT1 and AT2 receptors are covalently labeled before being subjected to enzymatic (V8 protease, Endo Lys-C, kallikrein, trypsin, etc.) or chemical digestions (CNBr). The radiolabeled fragment genereted with a specific enzyme is then resolved by SDS-PAGE electrophoresis and autoradiography. The sequence of the labeled fragment is deduced from its apparent size. The exact residue on the receptor interacting with the photosensitive ligand may be identified by Edman reaction cycles on the shortest fragment generated. With three photosensitive analogs of AngII in which Asp1, Val3 or Phe8 were substituted for Bpa, we demonstrated that the N-terminal part of AngII interacts with the extracellular tail of AT2 receptor and with the second extracellular loop of AT1 receptor whereas the C-terminal part of AngII interacts with the third transmembrane domain of AT2 receptor and with the seventh transmembrane domain of AT1 receptor. These results added to those expected with other photosensitive analogs of AngII will provide valuable informations for drawing three-dimensional models of ligand/receptor interaction.

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Presentation Number SAguillemette,0679
Keywords: Angiotensin II, Receptor, Binding pocket, Photoaffinity