菌紫质是一种强大的光驱动质子泵。
Bacteriorhodopsin is a powerful light-driven proton pump.
出版信息
Biophys J. 1987 May;51(5):839-41. doi: 10.1016/S0006-3495(87)83411-2.
The activity of bacteriorhodopsin was investigated with Halobacterium halobium cell envelopes, which lack cytoplasmic constituents. It was found that the physiological concentration of magnesium ion greatly enhanced the light-induced pH change; under optimal conditions, the pH change of the external medium was as large as 3.5 pH units, even though the volume fraction of the envelope vesicles was as low as 0.01. This pH change is about three times larger than the largest change reported thus far. This same effect was observed with transition metal ions, but not with other alkaline divalent cations. That is, divalent cations that formed hydroxides below pH 10 were effective in enhancing the light-induced pH change. This result suggests that some divalent cations acted as buffers against a large increase in the internal pH, and that the internal pH was an important factor in determining the activity of bacteriorhodopsin. It was also shown that a high level of the proton-pump activity was maintained in a wide range of external pHs, at least between 4.5 and 9.4.
用缺乏细胞质成分的嗜盐菌细胞包膜研究了菌紫质的活性。结果发现生理浓度的镁离子大大增强了光诱导的 pH 变化；在最佳条件下，外部介质的 pH 变化高达 3.5 pH 单位，尽管包膜囊泡的体积分数低至 0.01。这个 pH 变化大约是迄今为止报道的最大变化的三倍。同样的效果也在过渡金属离子中观察到，但在其他碱性二价阳离子中则没有观察到。也就是说，在 pH 低于 10 时形成氢氧化物的二价阳离子能够有效地增强光诱导的 pH 变化。这一结果表明，某些二价阳离子起到了缓冲内部 pH 大幅增加的作用，而内部 pH 是决定菌紫质活性的一个重要因素。还表明，在广泛的外部 pH 值范围内，至少在 4.5 到 9.4 之间，质子泵的活性保持在较高水平。
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