Sar1-p-benzoylphenylalanine-angiotensin, a new photoaffinity probe for selective labeling of the type 2 angiotensin receptor.
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.
Bossé
R
R
Department of Pharmacology, Faculty of Medicine, University of Sherbrooke, Canada.
Servant
G
G
Zhou
L M
LM
Boulay
G
G
Guillemette
G
G
Escher
E
E
D000302:Adrenal Cortex / Q000378:metabolism; D000345:Affinity Labels / Q000378:metabolism*; D000804:Angiotensin II / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D001011:Aorta; D001667:Binding, Competitive; D002417:Cattle; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D007093:Imidazoles / Q000378:metabolism / Q000494:pharmacology; D066298:In Vitro Techniques; D009215:Myometrium / Q000378:metabolism; D011725:Pyridines / Q000378:metabolism / Q000494:pharmacology; D011817:Rabbits; D011945:Receptors, Angiotensin / Q000378:metabolism*; D013777:Tetrazoles / Q000378:metabolism / Q000494:pharmacology; D015384:Zona Glomerulosa / Q000166:cytology / Q000378:metabolism
D000345:Affinity Labels; D057911:Angiotensin Receptor Antagonists; D007093:Imidazoles; D011725:Pyridines; D011945:Receptors, Angiotensin; D013777:Tetrazoles; D000804:Angiotensin II; C073402:PD 123319; C070967:L 158809