Clague M J, Knutson J R, Blumenthal R, Herrmann A
Section of Membrane Structure and Function, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892.
Biochemistry. 1991 Jun 4;30(22):5491-7. doi: 10.1021/bi00236a023.
We have studied tryptophan fluorescence from a 20-residue synthetic peptide corresponding to the amino terminal of the HA2 subunit of the influenza virus hemagglutinin protein, a putative "fusion" peptide. Decay-associated spectra have been obtained at pH 7.4 and at pH 5 (the optimal pH for influenza virus fusion) in the presence and absence of liposomes. We demonstrate that a blue shift in the total steady-state fluorescence spectrum upon binding to liposomes is due to a movement in characteristic emission wavelength and increased lifetime of one of the resolved spectral components. In contrast, a further shift after lowering the pH is the product of a redistribution in the relative amplitudes of spectral components. Also, each decay component is quenched by spin-labels or anthroxyl groups normally located within the hydrocarbon interior of the membranes. Calculations are presented leading to an estimate of the distance of the tryptophan residue from the bilayer center, suggesting that the tryptophan residues are at or near the hydrocarbon-polar interface. No gross positional change was detected between pH values. Rotational depolarization is shown to be retarded by liposome binding, more so at low pH.
我们研究了来自一种20个残基的合成肽的色氨酸荧光，该肽对应于流感病毒血凝素蛋白HA2亚基的氨基末端，即一种假定的“融合”肽。在有脂质体和无脂质体的情况下，分别在pH 7.4和pH 5（流感病毒融合的最佳pH）条件下获得了衰减相关光谱。我们证明，与脂质体结合后总稳态荧光光谱的蓝移是由于特征发射波长的移动以及其中一个分辨光谱成分寿命的延长。相比之下，降低pH后进一步的光谱移动是光谱成分相对振幅重新分布的结果。此外，每个衰减成分都会被通常位于膜烃类内部的自旋标记或蒽基淬灭。文中给出了相关计算，据此估算了色氨酸残基与双层中心的距离，这表明色氨酸残基处于烃类-极性界面处或其附近。在不同pH值之间未检测到明显的位置变化。结果表明，脂质体结合会使旋转去极化受到阻碍，在低pH时这种阻碍作用更明显。
