Schiller P W
Can J Biochem. 1977 Jan;55(1):75-82. doi: 10.1139/o77-013.
[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.
[色氨酸1，缬氨酸5]-血管紧张素II通过固相法合成，并通过在葡聚糖凝胶G-25上的分配色谱法和在葡聚糖凝胶SP-25上的离子交换色谱法进行纯化。相对于[缬氨酸5]-血管紧张素II，该类似物在肠系膜上动脉制剂中表现出36%的平滑肌活性。通过荧光技术揭示了该类似物的构象方面。在350nm处的最大荧光发射表明[色氨酸1，缬氨酸5]-血管紧张素II中色氨酸残基处于完全水相环境。基于Förster方程，评估了4位酪氨酸与1位色氨酸之间的单重态-单重态共振能量转移，以计算这两个残基之间的分子内距离。从色氨酸荧光的相对增加中获得了大于0.9的转移效率，这与该类似物中酪氨酸荧光的完全淬灭相一致。计算出的平均分子内距离小于8埃，排除了在中性pH下包含1至4位残基的N端序列的伸展构象，并表明在分子的这一部分存在一个环。结合为血管紧张素II的溶液构象提出的各种模型对结果进行了讨论。
