Light-driven chloride ion transport by halorhodopsin from Natronobacterium pharaonis. 1. The photochemical cycle.
Light-driven chloride ion transport by halorhodopsin from Natronobacterium pharaonis. 1. The photochemical cycle.
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DOI：
10.1021/bi00044a027
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发表时间：
1995-11
期刊：
影响因子：
2.9
通讯作者：
G. Varo;L. Brown;J. Sasaki;H. Kandori;A. Maeda;R. Needleman;J. Lanyi
中科院分区：
文献类型：
--
作者：
G. Varo;L. Brown;J. Sasaki;H. Kandori;A. Maeda;R. Needleman;J. Lanyi
在可见光和红外下，用瞬时光学多通道和单波长光谱描述了光驱动氯泵的光化学循环。加入氯化物后吸收极大值蓝移的滴定描述了Kd值为1 mm的结合位置。这种氯结合形式的视网膜在全反式到13-顺式光异构化后的反应序列本身依赖于氯。在2M氯化物中，它被描述为：HR-->；Kln-->；HR在几毫秒内松弛，非常类似于在视网膜席夫碱不能去质子化的条件下细菌视紫红质的光循环。然而，在较低的氯浓度下，例如0.1M，在N和HR之间出现一个红移态O，与N平衡。K、L、N和O的吸收光谱与它们在细菌视紫红质光循环中的吸收光谱非常相似。与细菌视紫红质的等价物一样，在N状态下，视网膜仍然是13顺式的，但它在O状态下被重新异构化为全反式。
The photochemical cycle of the light-driven chloride pump, halorhodopsin from N. pharaonis, is described by transient optical multichannel and single-wavelength spectroscopy in the visible, and in the infrared. Titration of a blue-shift of the absorption maximum upon addition of chloride describes a binding site with a KD of 1 mM. The reaction sequence after the all-trans to 13-cis photoisomerization of the retinal in this chloride binding form is itself dependent on chloride. At 2 M chloride it is described by the scheme: HR-->KLN-->HR that relaxes in a few milliseconds, and is very similar to the photocycle of bacteriorhodopsin under conditions where the retinal Schiff base cannot deprotonate. At lower chloride concentrations, e.g., 0.1 M, however, a red-shifted state termed O appears between N and HR, in equilibrium with N. The absorption spectra of K, L, N, and O are very similar to their counterparts in the bacteriorhodopsin photocycle. As in their equivalents in bacteriorhodopsin, in the N state the retinal is still 13-cis, but it is reisomerized in the O state to all-trans.