The conformational properties of the first extracellular (EL1) and third (ytosolic (IL3) loops, and of the C-terminal region (CT) of the angiotensin II AT1 receptor were investigated by means of CD, fluorescence and 2D 1H-NMR spectra of synthetic peptides, in aqueous solution, as a function of ptI, temperature, and peptide and salt concentration. The effect of TFE and the binding of the peptides to model membranes were also examined. The conformations found were in agreement with predictions for these regions in the whole protein. Thus, EL1 (containing Y92, essential for hormone binding) formed a stable turn, the N-terminal region of IL3 (important for G protein activation) was largely α-helical, while its C-terminal portion (not important for G protein activation) was less structured: CT (which activates G protein) was predominantly α- helical. The α-helical content was a function of the experimental conditions. Addition of TFE and binding to model membranes increased peptide secondary structure. Fluorescence data suggested that the peptides are located at the water-membrane interface. The conformational changes observed in the present study could be involved in different steps of signal transduction, such as ligand binding and G protein activation.
|Publication status||Published - 1997|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology