title: The conformation of angiotensin II. II. The rates of peptide NH exchange with solvent for [Asn1, Val5]angiotensin II, angiotensin III and saralasin.
abstract: The amide hydrogen exchange rates in H2O of two angiotensin agonists (angiotensinamide and angiotensin III) and one angiotensin antagonist (saralasin) have been measured at room temperature by the transfer of solvent saturation method. The NH of His6 is observed to exchange more slowly than predicted for all three peptides, suggesting that it is a participant in an intramolecular hydrogen bond. The NH-C alpha H 1H-NMR coupling constants are measured and found to be constant over the pH range of 5.0 to 6.5. The results are compared with those previously obtained for human angiotensin II and interpreted in terms of a dominant three-dimensional structure common to all four molecules. Two models for this structure are evaluated using the observed NH-C alpha H coupling constants and the reported activity of conformationally restrained derivatives.
mesh_terms: D000802:Angiotensin Amide; D000804:Angiotensin II / Q000031:analogs & derivatives*; D000805:Angiotensin III; D000809:Angiotensins / Q000037:antagonists & inhibitors; D055598:Chemical Phenomena; D002621:Chemistry; D006801:Humans; D006859:Hydrogen; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008433:Mathematics; D011487:Protein Conformation; D012504:Saralasin
chemical_list: D000809:Angiotensins; D000804:Angiotensin II; D000805:Angiotensin III; D000802:Angiotensin Amide; D006859:Hydrogen; D012504:Saralasin