Cation binding by bacteriorhodopsin.
Cation binding by bacteriorhodopsin.
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细菌视紫红质结合阳离子。
DOI：
10.1073/pnas.82.2.396
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发表时间：
1985
影响因子：
11.1
通讯作者：
T. Ebrey
中科院分区：
文献类型：
--
作者：
C. Chang;J. G. Chen;R. Govindjee;T. Ebrey
我们发现，广泛洗涤的紫色膜每个细菌视紫红质分子约有1个钙离子和3-4个镁离子结合。当这些二价阳离子通过任何一种方法被去除时，色素的颜色从紫色变为蓝色（λ (max)约为600 nm）。这种蓝色色素可以在接近中性的pH值下形成，可能与紫色膜样品的pH值降低到大约2时形成的蓝色色素非常相似。当将多种阳离子中的任何一种加入到蓝色膜制剂中时，细菌视紫红质的紫色特征就会恢复。二价和三价阳离子在恢复紫色方面比一价阳离子更有效，并且在接近每个色素分子一个阳离子的比例下有效。除了改变吸收光谱外，去除二价阳离子还会极大地改变细菌视紫红质的光化学循环，包括取消未质子化的希夫碱（m型）中间体。最后，镧不仅取代了通常结合在紫色膜上的二价阳离子，而且大大降低了M412中间体的衰变速度和质子摄取速度。
We have found that extensively washed purple membrane has about 1 calcium and 3-4 magnesium ions bound per bacteriorhodopsin molecule. When these divalent cations are removed by any of a variety of means, the pigment changes its color from purple to blue (lambda(max) approximately 600 nm). This blue pigment, which can be formed at near neutral pH, is probably very similar to blue species formed when the pH of a purple membrane sample is lowered to approximately 2. When any of a wide variety of cations are added to a blue membrane preparation, the characteristic purple color of bacteriorhodopsin returns. Divalent and trivalent cations are much more efficient than monovalent cations in restoring the purple color and are effective at a ratio approaching one cation per pigment molecule. Besides shifting the absorption spectrum, removal of the divalent cations drastically alters the photochemical cycle of bacteriorhodopsin, including abolishing the unprotonated Schiff base (M-type) intermediate. Finally, lanthanum not only displaces the divalent cations normally bound to the purple membrane but also greatly reduces both the rate of decay of the M412 intermediate and proton uptake.