Structure of two fragments of the third cytoplasmic loop of the rat angiotensin II AT(1A) receptor: Implications with respect to receptor activation and G-protein selection and coupling

Lorella Franzoni, Giuseppe Nicastro, Thelma A. Pertinhez, Eliandre Oliveira, Clóvis R. Nakaie, Antonio C M Paiva, Shirley Schreier, Alberto Spisni

Research output: Contribution to journalArticle

Abstract

The structural bases that render the third intracellular loop (i3) of the rat angiotensin II AT(1A) receptor one of the cytoplasmic domains responsible for G-protein coupling are still unknown. The three-dimensional structures of two overlapping peptides mapping the entire i3 loop and shown to differently interact with purified G-proteins have been obtained by simulated annealing calculations, using NMR-derived constraints collected in 70% water/30% trifluoroethanol solution. While the NH2-terminal half, Ni3, residues 213-231, adopts a stable amphipathic α-helix, extending over almost the entire peptide, a more flexible conformation is found for the COOH- terminal half, Ci3, residues 227-242. For this peptide, a cis-trans isomerization around the Lys6-Pro7 peptide bond generates two exchanging isomers adopting similar conformations, with an α-helix spanning from Asn9 to Ile15 and a poorly defined NH2 terminus. A quite distinct structural organization is found for the sequence EIQKN, common to Ni3 and Ci3. The data do suggest that the extension and orientation of the amphipathic α-helix, present in the proximal part of i3, may be modulated by the distal part of the loop itself through the Pro233 residue. A molecular model where this possibility is considered as a mechanism for G-protein selection and coupling is presented.

Original languageEnglish
Pages (from-to)227-235
Number of pages9
JournalJournal of Biological Chemistry
Volume274
Issue number1
DOIs
Publication statusPublished - Jan 1 1999

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GTP-Binding Proteins
Angiotensin II
Rats
Chemical activation
Peptides
Trifluoroethanol
Conformations
Molecular Models
Peptide Mapping
Cytoplasmic and Nuclear Receptors
Chemical bonds
Isomerization
Simulated annealing
Isomers
Water
Nuclear magnetic resonance

ASJC Scopus subject areas

  • Biochemistry

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Structure of two fragments of the third cytoplasmic loop of the rat angiotensin II AT(1A) receptor : Implications with respect to receptor activation and G-protein selection and coupling. / Franzoni, Lorella; Nicastro, Giuseppe; Pertinhez, Thelma A.; Oliveira, Eliandre; Nakaie, Clóvis R.; Paiva, Antonio C M; Schreier, Shirley; Spisni, Alberto.

In: Journal of Biological Chemistry, Vol. 274, No. 1, 01.01.1999, p. 227-235.

Research output: Contribution to journalArticle

Franzoni, Lorella ; Nicastro, Giuseppe ; Pertinhez, Thelma A. ; Oliveira, Eliandre ; Nakaie, Clóvis R. ; Paiva, Antonio C M ; Schreier, Shirley ; Spisni, Alberto. / Structure of two fragments of the third cytoplasmic loop of the rat angiotensin II AT(1A) receptor : Implications with respect to receptor activation and G-protein selection and coupling. In: Journal of Biological Chemistry. 1999 ; Vol. 274, No. 1. pp. 227-235.
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