Sar1-p-benzoylphenylalanine-angiotensin, a new photoaffinity probe for selective labeling of the type 2 angiotensin receptor

Regul Pept. 1993 Mar 19;44(2):215-23. doi: 10.1016/0167-0115(93)90245-4.

Abstract

Previous photoaffinity labeling of angiotensin II (Ang) receptors with azidophenylalanine containing Ang analogs produced high yield labeling of a 60 kDa protein on bovine adrenocortical membranes. This preparation is mostly enriched in the type 1 Ang receptor (AT1) and AT1 selective ligands (L158,809) totally prevented labeling, therefore confirming the AT1 nature of the labeled protein. Our attempt to photolabel the type 2 Ang receptor (AT2) of human myometrium with [Sar1,D-Phe(N3)8]Ang was unsuccessful, revealing a high degree of photolabeling selectivity. An Ang analog, [Sar1,Bpa8]Ang (or BpaAng) was prepared containing the photosensitive amino acid p-benzoylphenylalanine (Bpa). This compound was a specific but non-competitive Ang antagonist on rabbit aorta with a pA2 of 8.5. It displayed good binding affinities for bovine adrenocortical membranes (Kd = 6.5 nM), a predominantly AT1 preparation, and for human myometrium membranes (Kd = 0.39 nM), a predominantly AT2 preparation. Photolabeling experiments with iodinated BpaAng showed that AT1 was not covalently labeled whereas AT2 was covalently labeled with high yield. Labeling specificity was verified with the AT2-selective ligand PD123319 and with the AT1-selective antagonist L158,809. Our results indicate that 125I-BpaAng is exclusively labeling AT2 sites. This compound should be a useful tool for further biochemical characterization of the AT2 binding site.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenal Cortex / metabolism
  • Affinity Labels / metabolism*
  • Angiotensin II / analogs & derivatives
  • Angiotensin II / metabolism*
  • Angiotensin II / pharmacology
  • Angiotensin Receptor Antagonists
  • Animals
  • Aorta
  • Binding, Competitive
  • Cattle
  • Cells, Cultured
  • Female
  • Humans
  • Imidazoles / metabolism
  • Imidazoles / pharmacology
  • In Vitro Techniques
  • Myometrium / metabolism
  • Pyridines / metabolism
  • Pyridines / pharmacology
  • Rabbits
  • Receptors, Angiotensin / metabolism*
  • Tetrazoles / metabolism
  • Tetrazoles / pharmacology
  • Zona Glomerulosa / cytology
  • Zona Glomerulosa / metabolism

Substances

  • Affinity Labels
  • Angiotensin Receptor Antagonists
  • Imidazoles
  • Pyridines
  • Receptors, Angiotensin
  • Tetrazoles
  • Angiotensin II
  • PD 123319
  • L 158809