Electric-field-induced Schiff-base deprotonation in D85N mutant bacteriorhodopsin
Electric-field-induced Schiff-base deprotonation in D85N mutant bacteriorhodopsin
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DOI：
10.1073/pnas.93.21.11618
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发表时间：
1996-10-15
影响因子：
11.1
通讯作者：
Rousseau, DL
中科院分区：
文献类型：
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作者：
Kolodner, P;Lukashev, EP;Rousseau, DL
对Asp-85 --> Asn突变菌视紫红质的干膜施加外电场会引起Schiff碱的去质子化，导致最大光吸收从600 nm移至400 nm。这与野生型细菌视紫红质膜的情况形成鲜明对比，在野生型细菌视紫红质膜中，电场产生红移产物，其光学性质与酸性蓝形式的蛋白质的光学性质相似。这种差异是由于突变蛋白质中席夫碱质子的结合弱得多，如其低pK（约为9）所示，而野生型中的pK值约为13。具有降低的席夫碱pK值的其他细菌视紫红质也应该在席夫碱的质子化平衡中表现出场诱导的移动。我们提出的机制来解释这些意见。
The application of an external electric field to dry films of Asp-85 --> Asn mutant bacteriorhodopsin causes deprotonation of the Schiff base, resulting in a shift of the optical absorption maximum from 600 nm to 400 nm. This is in marked contrast to the case of wild-type bacteriorhodopsin films, in which electric fields produce a red-shifted product whose optical properties are similar to those of the acid-blue form of the protein. This difference is due to the much weaker binding of the Schiff-base proton in the mutant protein, as indicated by its low pK of approximate to 9, as compared with the value pK approximate to 13 in the wild type. Other bacteriorhodopsins with lowered Schiff-base pK values should also exhibit a field-induced shift in the protonation equilibrium of the Schiff base. We propose mechanisms to account for these observations.