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Title: Structure of two fragments of the third cytoplasmic loop of the rat angiotensin II AT(1A) receptor
Authors: Franzoni, Lorella
Nicastro, Giuseppe
Pertinhez, Thelma A.
Oliveira, Eliandre [UNIFESP]
Nakaie, Clovis Ryuichi [UNIFESP]
Paiva, Antonio Cechelli de Mattos [UNIFESP]
Schreier, Shirley
Spisni, Alberto
Univ Parma
Universidade de São Paulo (USP)
Universidade Federal de São Paulo (UNIFESP)
Issue Date: 1-Jan-1999
Publisher: Amer Soc Biochemistry Molecular Biology Inc
Citation: Journal of Biological Chemistry. Bethesda: Amer Soc Biochemistry Molecular Biology Inc, v. 274, n. 1, p. 227-235, 1999.
Abstract: The structural bases that render the third intracellular loop (i3) of the rat angiotensin II AT,, 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 alpha-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 Lys(6)-Pro(7) peptide bond generates two exchanging isomers adopting similar conformations, with an ct-helix spanning from Asn(9) to Ile(15) and a poorly defined NH, 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 cu-helix, present in the proximal part of i3, may be modulated by the distal part of the loop itself through the Pro(233) residue. A molecular model where this possibility is considered as a mechanism for G-protein selection and coupling is presented.
ISSN: 0021-9258
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