The octapeptide angiotensin II adopts a well-defined structure in a phospholipid environment.
The conformational properties adopted by angiotensin II in a phospholipid micelle solution were studied by NMR spectroscopy and molecular modelling. The octapeptide was found to assume a well-defined hairpin structure with its C- and N-termini approaching to within 0.76 nm of each other. Three of the residues had fixed side chain configurations; Tyr4 (g+), His6 (g-) and Val3 (g-). Consequently, the His6 and Tyr4 aromatic rings were consistently close together. Conformers containing a cis His6-Pro7 peptide bond were observed for the peptide in a purely aqueous sample but completely disappeared when lipid vesicles were added to the sample. This result is explained by the existence of a very stable hydrogen bond between the Phe8 NH and the His6 carbonyl group of the lipid-solvated trans isomer, resulting in the formation of an inverse gamma turn centered on Pro7. 1H-NMR selective line broadening was apparent for several of the angiotensin II protons upon titration of an aqueous sample with less than stoichiometric amounts of 1,2-dimyristoyl-sn-glycero-3-phosphocholine bilayer vesicles. The data obtained were consistent with the structure derived for micelle-bound angiotensin II, indicating that conformations adopted by the peptide hormone in the presence of micelles and lipid-bilayer vesicles are similar.
Carpenter
K A
KA
Laboratory of Chemical Biology and Peptide Research, Clinical Research Institute of Montreal, Quebec, Canada.
Wilkes
B C
BC
Schiller
P W
PW
D000804:Angiotensin II / Q000737:chemistry* / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry / Q000378:metabolism; D008051:Lipid Bilayers; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D008958:Models, Molecular; D010743:Phospholipids / Q000737:chemistry* / Q000378:metabolism; D010767:Phosphorylcholine / Q000031:analogs & derivatives / Q000737:chemistry; D011487:Protein Conformation; D014867:Water
D008051:Lipid Bilayers; D008823:Micelles; D010743:Phospholipids; D014867:Water; D010767:Phosphorylcholine; D000804:Angiotensin II; C028810:dodecylphosphocholine; D004134:Dimyristoylphosphatidylcholine