Synthesis and solution conformation of [Trp1, Val5]-angiotensin II.
[Trp1, Val5]-Angiotensin II was synthesized by the solid-phase method and purified by partition chromatography on Sephadex G-25 and by ion-exchange chromatography on Sephadex SP-25. Relative to [Val5]-angiotensin II, the analog displayed 36% smooth muscle activity in a preparation of the superior mesenteric artery. Conformational aspects of the analog were revealed by fluorescence techniques. The fluorescence emission maximum at 350 nm suggests a completely aqueous environment for the tryptophanyl residue in [Trp1, Val5]-angiotensin II. Singlet-singlet resonance energy transfer between Tyr in position 4 and Trp in position 1 was evaluated for a calculation of the intramolecular distance between these two residues on the basis of the Förster equation. From the relative increase of tryptophan fluorescence a transfer efficiency of greater 0.9 was obtained, which is compatible with the observed complete quenching of tyrosine fluorescence in the analog. The computed average intramolecular distance of less than 8 A precludes an extended conformation for the N-terminal sequence encompassing residues 1 through 4 at neutral pH and suggests the existence of a loop in this part of the molecule. The results are discussed in relation to the various models proposed for the solution conformation of angiotensin II.
D000804:Angiotensin II / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D002852:Chromatography, Ion Exchange; D004735:Energy Transfer; D008433:Mathematics; D008722:Methods; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D014364:Tryptophan; D014633:Valine
D000804:Angiotensin II; D014364:Tryptophan; D014633:Valine