Short peptide constructs mimic agonist sites of AT^sub 1^R and BK receptors

• Published in: Amino acids Vol. 44; no. 3; p. 835
• Main Authors: Lopes, Douglas D, Vieira, Renata F; F, Malavolta, Luciana, Poletti, Erick F, Shimuta, Suma I, Paiva, Antonio C; M, Schreier, Shirley, Oliveira, Laerte, Nakaie, Clovis R
• Format: Journal Article
• Language: English
• Published: Vienna Springer Nature B.V 01.03.2013
• ISSN: 0939-4451; 1438-2199
• DOI: 10.1007/s00726-012-1405-9

Extracellular peptide ligand binding sites, which bind the N-termini of angiotensin II (AngII) and bradykinin (BK) peptides, are located on the N-terminal and extracellular loop 3 regions of the AT^sub 1^R and BKRB^sub 1^ or BKRB^sub 2^ G-protein-coupled receptors (GPCRs). Here we synthesized peptides P15 and P13 corresponding to these receptor fragments and showed that only constructs in which these peptides were linked by S-S bond, and cyclized by closing the gap between them, could bind agonists. The formation of construct-agonist complexes was revealed by electron paramagnetic resonance spectra and fluorescence measurements of spin labeled biologically active analogs of AngII and BK (Toac^sup 1^-AngII and Toac^sup 0^-BK), where Toac is the amino acid-type paramagnetic and fluorescence quencher 2, 2, 6, 6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid. The inactive derivatives Toac^sup 3^-AngII and Toac^sup 3^-BK were used as controls. The interactions characterized by a significant immobilization of Toac and quenching of fluorescence in complexes between agonists and cyclic constructs were specific for each system of peptide-receptor construct assayed since no crossed reactions or reaction with inactive peptides could be detected. Similarities among AT, BKR, and chemokine receptors were identified, thus resulting in a configuration for AT^sub 1^R and BKRB cyclic constructs based on the structure of the CXCR^sub 4^, an [alpha]-chemokine GPCR-type receptor.[PUBLICATION ABSTRACT]