固氮红细菌(Rhodobacter azotoforman)色素蛋白复合体的分离纯化与特性

【目的】为揭示不产氧光合细菌产氢菌株色素蛋白复合体(PPC)色素组成和含量与光合放氢的关系奠定基础。【方法】以PPC特征光谱为检测指标,采用硫酸铵分级分离、DEAE-纤维素层析、吸收光谱和SDS-PAGE等方法进行了固氮红细菌(Rhodobacter azotoformans,R.azotoformans)R7产氢菌株PPC的分离纯化、纯度分析和鉴定;采用表面增强激光解吸电离离子飞行时间质谱、HPLC-MS和荧光光谱法对其中一种PPC进行了组成分析和能量传递活性测定。【结果】从R7菌株获得了3种纯化的PPC,1种为反应中心与中心捕光色素蛋白复合体(RC-LH1),2种为外周捕光色素蛋白复合体(LH2),其中一种LH2的吸收光谱具有异常的423nm强吸收峰,其蛋白的两种亚基的分子量分别为5356.8Da和5697.8Da,类胡萝卜素属球形烯系,分子量为562Da,激发光能够从类胡萝卜素向细菌叶绿素以及细菌叶绿素向细菌叶绿素传递。【结论】固氮红细菌产氢菌株含有2种不同光谱特性的LH2,其中一种具有新光谱特性。

Isolation and characterization of pigment-protein complexes from Rhodobacter azotoformans

Abstract: Objective] In order to reveal the relationships of compositions and content of pigment in pigment-protein complexes (PPC) and hydrogen photoevolution from anoxygenic phototrophic bacteria. Methods] We isolated and identified pigment-protein complexes using a separation strategy of subsequent fractionated ammonium-sulfate precipitation, ion exchange column chromatography, absorption spectra and sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) from hydrogen-producing Rhodobacter azotoformans R7. We investigated the characterizations of the peripheral light-harvesting complex (LH2) with an unusual absorption spectrum by surface enhanced laser desorption / ionization time of flight mass spectrometry (SELDI-TOF-MS), high performance liquid chromatography-mass spectrometry (HPLC-MS) and fluorescence spectra. Results] We acquired three types of PPC, the reaction center and core light-harvesting complex (RC-LH1) and two kinds of LH2, from strain R7 incubated anaerobically in the light. The two LH2 showed the different absorption spectra, one of them displayed unusual absorption spectrum with the maximum absorption band at 423 nm. The unusual LH2 consisted of two kinds of protein subunits with the molecular weight of 5556.8 Da and 5697.8 Da and carotenoid of spheroidene series with the molecular weight of 562 Da. It was also capable of transferring energy from carotenoid to bacterialcholorophyll and from B800 bacterialcholorophyll to B850 bacterialcholorophyll. Conclusion] Rhodobacter azotoformans R7 with hydrogen-producing capacity could photosynthesize two types of LH2 under anaerobically in the light, one of them presented novel spectral property.