Unfolding pathways of native bacteriorhodopsin depend on temperature
Unfolding pathways of native bacteriorhodopsin depend on temperature
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DOI：
10.1093/emboj/cdg509
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发表时间：
2003-10-01
期刊：
影响因子：
11.4
通讯作者：
Müller, DJ
中科院分区：
文献类型：
--
作者：
Janovjak, H;Kessler, M;Müller, DJ
结合高分辨率原子力显微镜（AFM）成像和单分子力谱展开单一的细菌视紫红质（BR）从天然紫膜补丁在各种生理相关的温度。展开光谱揭示了详细的洞察BR对机械展开的各个结构元素的稳定性。解折叠过程中的间歇状态与α-螺旋的逐步解折叠相关，而其他状态与连接α-螺旋的多肽环的解折叠相关。结果表明，当温度从8 ℃升高到52 ℃时，二级结构的解折叠力显著降低。与此相关的是，BR的个别解折叠途径的概率受到温度的显著影响。在较低的温度下，跨膜α-螺旋和细胞外多肽环表现出足够的稳定性，以单独建立潜在的障碍，对展开，而他们主要在高温下展开集体。这表明，增加温度降低了二级结构元件的机械稳定性，并改变了二级结构之间的分子相互作用，从而迫使它们作为分组结构。
The combination of high-resolution atomic force microscopy (AFM) imaging and single-molecule force-spectroscopy was employed to unfold single bacteriorhodopsins (BR) from native purple membrane patches at various physiologically relevant temperatures. The unfolding spectra reveal detailed insight into the stability of individual structural elements of BR against mechanical unfolding. Intermittent states in the unfolding process are associated with the stepwise unfolding of alpha-helices, whereas other states are associated with the unfolding of polypeptide loops connecting the alpha-helices. It was found that the unfolding forces of the secondary structures considerably decreased upon increasing the temperature from 8 to 52degreesC. Associated with this effect, the probability of individual unfolding pathways of BR was significantly influenced by the temperature. At lower temperatures, transmembrane alpha-helices and extracellular polypeptide loops exhibited sufficient stability to individually establish potential barriers against unfolding, whereas they predominantly unfolded collectively at elevated temperatures. This suggests that increasing the temperature decreases the mechanical stability of secondary structural elements and changes molecular interactions between secondary structures, thereby forcing them to act as grouped structures.