PROPERTIES OF A WATER-SOLUBLE, YELLOW PROTEIN ISOLATED FROM A HALOPHILIC PHOTOTROPHIC BACTERIUM THAT HAS PHOTOCHEMICAL ACTIVITY ANALOGOUS TO SENSORY RHODOPSIN
PROPERTIES OF A WATER-SOLUBLE, YELLOW PROTEIN ISOLATED FROM A HALOPHILIC PHOTOTROPHIC BACTERIUM THAT HAS PHOTOCHEMICAL ACTIVITY ANALOGOUS TO SENSORY RHODOPSIN
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DOI：
10.1021/bi00376a012
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发表时间：
1987-01-27
期刊：
影响因子：
2.9
通讯作者：
TOLLIN, G
中科院分区：
文献类型：
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作者：
MEYER, TE;YAKALI, E;TOLLIN, G
先前在紫色光合细菌 Ectothiorhodospira halophila 中发现的一种水溶性黄色蛋白质，含有一个在 446 nm 处具有最大吸光度的发色团。现在该蛋白质被证明具有光活性。 445 nm 激光脉冲导致 446 nm 峰在不到 1 μs 的时间内部分漂白和红移。由此形成的中间体随后在大约 20 ms 内发生的双相过程中在黑暗中进一步漂白。最后，天然蛋白质的吸光度在几秒钟内发生的一级过程中恢复。这些动力学过程与来自盐杆菌的感觉视紫红质的动力学过程非常相似，并且在较小程度上与细菌视紫红质和盐酸盐视紫红质相似。尽管这些蛋白质是膜结合的，但它们在约 570 nm 处具有最大吸光度，并且循环速度更快。在尝试去除发色团进行鉴定时，发现多种蛋白质变性方法会导致瞬时或永久转化为在 340 nm 附近具有最大吸光度的形式。因此，与视紫红质类比，天然蛋白质中 446 nm 处的吸收似乎是由蛋白质诱导的发色团 106 nm 红移引起的。酸变性，然后用有机溶剂萃取，确定可以从蛋白质中除去发色团。它与全反式视网膜不同，尽管它可能是一种相关的色素，但仍有待鉴定。嗜盐大肠杆菌黄色蛋白具有圆二色光谱，表明很少有α-螺旋二级结构(19％)。尽管黄色蛋白的性质独特，但它同时具有细菌视紫红质（就光化学而言）和动物视黄醇结合蛋白（就溶解度而言）的特征。
A water-soluble yellow protein, previously discovered in the purple photosynthetic bacterium Ectothiorhodospira halophila, contains a chromophore which has an absorbance maximum at 446 nm. The protein is now shown to be photoactive. A pulse of 445-nm laser light caused the 446-nm peak to be partially bleached and red-shifted in a time less than 1 .mu.s. The intermediate thus formed was subsequently further bleached in the dark in a biphasic process occurring in approximately 20 ms. Finally, the absorbance of native protein was restored in a first-order process occurring over several seconds. These kinetic processes are remarkably similar to those of sensory rhodopsin from Halobacterium, and to a lesser extent bacteriorhodopsin and halorhodopsin; although these proteins are membrane-bound, they have absorbance maxima at about 570 nm, and they cycle more rapidly. In attempts to remove the chromophore for identification, it was found that a variety of methods of denaturation of the protein caused transient or permanent conversion to a form which has an absorbance maximum near 340 nm. Thus, by analogy to the rhodopsins, the absorption at 446 nm in the native protein appears to result from a 106-nm red shift of the chromophore induced by the protein. Acid denaturation followed by extraction with organic solvents established that the chromophore could be removed from the protein. It is not identical with all-trans-retinal and remains to be identified, although it could sitll be a related pigment. The E. halophila yellow protein has a circular dichroism spectrum which indicates little .alpha.-helical secondary structure (19%). Although the yellow protein is unique in its properties, it has characteristics of both bacterial rhodopsins (in terms of photochemistry) and the animal retinol binding proteins (in terms of solubility).