Photoreaction cycle of photoactive yellow protein from Ectothiorhodospira halophila studied by low-temperature spectroscopy
Photoreaction cycle of photoactive yellow protein from Ectothiorhodospira halophila studied by low-temperature spectroscopy
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DOI：
10.1021/bi961342d
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发表时间：
1996-11-12
期刊：
影响因子：
2.9
通讯作者：
Tokunaga, F
中科院分区：
文献类型：
--
作者：
Imamoto, Y;Kataoka, M;Tokunaga, F
采用低温光谱法研究了嗜盐外硫红螺菌的光活性黄色蛋白（PYP）的光循环。 PYP 在 -190 摄氏度下的辐照产生了由红色和低色光产物（PYPB 和 PYPH）组成的光稳态混合物。升温后，PYPH 在 -150 摄氏度以上热转化为轻微蓝移中间体 (PYPHL)，然后在 -80 摄氏度以上转化为红移中间体 (PYPL)。在 -180 摄氏度以上，PYPB 热转化为蓝移中间体 (PYPBL)，然后在 -90 摄氏度以上转化为 PYPL。在 -50 摄氏度以上，PYPL 热还原为 PYP，完成光循环。低温下形成的 PYPL 的光谱特性表明它对应于室温下纳秒至微秒时间尺度检测到的红移光产物 (A(465))。估计了 PYPH、PYPB 和 PYPL 的绝对吸收光谱，并确定它们的最大吸收最大值分别为 -190 ℃ 下的 442 和 489 nm 以及 -80 ℃ 下的 456 nm。虽然在室温下从 A(465) 回收 PYP 的过程中观察到近紫外中间体 (A(355))，但在低温下未检测到，可能是由于温度和甘油存在的影响。提出了 PYP 光循环的方案。
The photocycle of photoactive yellow protein (PYP) from Ectothiorhodospira halophila was studied by low-temperature spectroscopy. Irradiation of PYP at -190 degrees C produced a photo-steady-state mixture composed of bathochromic and hypsochromic photoproducts (PYPB and PYPH). Upon warming, PYPH was thermally converted to a slightly blue-shifted intermediate (PYPHL) above -150 degrees C and then to a red-shifted one (PYPL) above -80 degrees C. PYPB was thermally converted to the blue-shifted intermediate (PYPBL) above -180 degrees C and then to PYPL above -90 degrees C. PYPL thermally reverted to PYP above -50 degrees C, completing the photocycle. The spectral properties of PYPL formed at low temperature suggest that it corresponds to the red-shifted photoproduct detected in the nano- to microsecond time scale at room temperature (A(465)) The absolute absorption spectra of PYPH, PYPB, and PYPL were estimated, and their absorption maxima were determined to be 442 and 489 nm at -190 degrees C and 456 nm at -80 degrees C, respectively. Although a near-UV intermediate (A(355)) is observed in the recovery process of PYP from A(465) at room temperature, it was not detected at low temperatures, probably due to the effects of temperature and the presence of glycerol. A scheme of the photocycle of PYP is presented.