Dependence of the hydration status of bacterial light-harvesting complex 2 on polyol cosolvents
Dependence of the hydration status of bacterial light-harvesting complex 2 on polyol cosolvents
复制标题
细菌光捕获复合物 2 的水合状态对多元醇共溶剂的依赖性
DOI：
10.1039/c6pp00270f
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发表时间：
2017
影响因子：
3.1
通讯作者：
Wang-Otomo Zheng-Yu
中科院分区：
文献类型：
--
作者：
Shi Ying;Yu Jie;Yu Long-Jiang;Wang Peng;Fu Li-Min;Zhang Jian-Ping;Wang-Otomo Zheng-Yu
低分子量（MW）多元醇是影响蛋白质结构和活性的有机渗透剂。我们打算研究低分子量多元醇对从光合细菌嗜热染色菌（Thermochromatium，Tch.）tepidum，一种生长在150 °C的嗜热菌。稳态光谱表明，增加甘油或山梨醇馏分高达60%（多元醇/水，v/v），类胡萝卜素（Crts）的可见光吸收保持不变，而近红外Qy吸收细菌叶绿素a（BChl）在800 nm（B800）和850 nm（B850）略有变化。进一步增加甘油（而不是山梨醇）的分数到80%（v/v）诱导的近红外吸收和荧光光谱的明显变化。瞬态吸收光谱表明，在BChl-Crt三重态能量转移过程中，B800和B850的Qy信号与Crt三重态（3Crt*）的动力学同相，这是由于3Crt*-BChl相互作用导致的Qy带位移。的稳态和瞬态光谱响应的Qy带被发现密切相关的水活性对多元醇的MW和混合比，这是合理化的C-和N-末端的LH 2的水合状态的变化。我们的研究结果表明，参考嗜温紫色细菌Rhodobacter sphaeroides 2.4.1，Tch。tepidum采用显著更强的LH 2水合作用来对抗低MW多元醇的渗透作用。
Low molecular weight (MW) polyols are organic osmolytes influencing protein structure and activity. We have intended to investigate the effects of low MW polyols on the optical and the excited-state properties of the light-harvesting complex 2 (LH2) isolated from the photosynthetic bacterium Thermochromatium (Tch.) tepidum, a thermophile growing at ∼50 °C. Steady state spectroscopy demonstrated that, on increasing glycerol or sorbitol fractions up to 60% (polyol/water, v/v), the visible absorption of carotenoids (Crts) remained unchanged, while the near infrared Qy absorption of bacteriochlorophyll a (BChl) at 800 nm (B800) and 850 nm (B850) varied slightly. Further increasing the fraction of glycerol (but not sorbitol) to 80% (v/v) induced distinct changes of the near infrared absorption and fluorescence spectra. Transient absorption spectroscopy revealed that, following the fast processes of BChl-to-Crt triplet energy transfer, rather weak Qy signals of B800 and B850 remained and evolved in phase with the kinetics of triplet excited state Crt (3Crt*), which are attributed to the Qy band shift as a result of 3Crt*–BChl interaction. The steady state and the transient spectral responses of the Qy bands are found to correlate intimately with the water activity varying against polyol MW and mixing ratio, which are rationalized by the change of the hydration status of the C- and N-termini of LH2. Our results suggest that, with reference to the mesophilic purple bacterium Rhodobacter sphaeroides 2.4.1, Tch. tepidum adopts substantially more robust LH2 hydration against the osmotic effects from the low MW polyols.