Thermal Adaptability of the Light-Harvesting Complex 2 from Thermochromatium tepidum : Temperature-Dependent Excitation Transfer Dynamics

作者：Ying Shi, Ningjiu Zhao, Peng Wang, Li-Min Fu, Long‐Jiang Yu, Jianping Zhang, Zheng‐Yu Wang‐Otomo · 发表于：The Journal of Physical Chemistry B · 年份：2015 · DOI：10.1021/acs.jpcb.5b09023 · 被引用次数：12 · 研究领域：Photosynthetic Processes and Mechanisms、Spectroscopy and Quantum Chemical Studies、Photoreceptor and optogenetics research

The photosynthetic purple bacterium Thermochromatium (Tch.) tepidum is a thermophile that grows at an optimal temperature of ∼50 °C. We have investigated, by means of steady-state and time-resolved optical spectroscopies, the effects of temperature on the near-infrared light absorption and the excitation energy transfer (EET) dynamics of its light-harvesting complex 2 (LH2), for which the mesophilic counterpart of Rhodobacter (Rba.) sphaeroides 2.4.1 (∼30 °C) was examined in comparison. In a limited range around the physiological temperature (10-55 °C), the B800-to-B850 EET process of the Tch. tepidum LH2, but not the Rba. sphaeroides LH2, was found to be characteristically temperature-dependent, mainly because of a temperature-tunable spectral overlap. At 55 °C, the LH2 complex from Tch. tepidum maintained efficient near-infrared light harvesting and B800-to-B850 EET dynamics, whereas this EET process was disrupted in the case of Rba. sphaeroides 2.4.1 owing to the structural distortion of the LH2 complex. Our results reveal a remarkable thermal adaptability of the light-harvesting function of Tch. tepidum, which could enhance our understanding of the survival strategy of this thermophile in response to environmental challenges.