Membrane Protein Stability: High Pressure Effects on the Structure and Chromophore-Binding Properties of the Light-Harvesting Complex LH2

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• 作者：Andrew Gall ; Aleksandr Ellervee ; James N. Sturgis ; Niall J. Fraser ; Richard J. Cogdell ; Arvi Freiberg ; and Bruno Robert
• 刊名：Biochemistry
• 出版年：2003
• 出版时间：November 11, 2003
• 年：2003
• 卷：42
• 期：44
• 页码：13019 - 13026
• 全文大小：168K
• 年卷期：v.42,no.44(November 11, 2003)
• ISSN：1520-4995

文摘

Using the bacteriochlorophyll a (Bchl) cofactors as intrinsic probes to monitor changes inmembrane protein structure, we investigate the response to high-pressure of the LH2 complexes from thephotosynthetic bacteria Rhodobacter sphaeroides 2.4.1 and Rhodopseudomonas acidophila 10050. ByFT-Raman spectroscopy, we demonstrate that high pressure does not induce significant distortion of theprotein-bound 850 nm-absorbing bacteriochlorophyll molecules, or break of the hydrogen bond they areinvolved in. This indicates in particular that the oligomerization of the polypeptides is not perturbed upto 0.6 GPa. The pressure-induced changes in the Bchl absorption spectra are attributed to pigment-pigment interactions. In contrast, the loss of 800 nm-absorbing bacteriochlorophyll reflects pressure-induced alterations to the tertiary structure of the protein in proximity to the membrane/cytosol interface.This suggests that the LH2 protein does have two independent structural domains. The first domain ispressure independent and comprises mostly the C-terminal domain. The second domain located on theN-terminal side exhibits sensitivity to pressure and pH reminiscent of soluble proteins. The LH2 thusconstitutes a suitable model system for studying in detail the stability of membrane-embedded hydrophobichelices and helices located at or close to the solvent/membrane interface.