LDAO对Rhodobacter azotoformans外周捕光复合体LH2构象及其细菌叶绿素解离行为的影响

Influence of LDAO on the Conformation and Release of Bacteriochlorophyll of Peripheral Light-Harvesting Complex (LH2) from Rhodobacter Azotoformans

为探求LDAO与LH2的相互作用关系和规律,深入认识LDAO对LH2结构和功能的影响。采用光谱法系统地研究了LDAO对Rhodobacter azotoformans134K20菌株LH2构象及其在极端环境中细菌叶绿素(BChl)解离行为的影响。结果表明:(1)在室温pH 8.0缓冲溶液中,LDAO导致LH2构象变化,α-螺旋含量提高,Tyr和B850细菌叶绿素特征峰蓝移,能量传递效率提高。(2)在60℃pH 8.0缓冲溶液中,LH2B800和B850细菌叶绿素可解离为游离BChl。LDAO能增加LH2的高温稳定性,延缓并改变B800和B850解离过程和行为。(3)在室温强酸和强碱溶液中,LDAO加剧了B800和B850的解离并分别转化为游离细菌脱镁叶绿素(BPhe)和游离BChl,表现出不同的解离行为。在不含LDAO的强酸溶液中,B850呈现先解离再自组装的过程。LDAO作用于LH2,可使其B800和B850在不同极端环境中的解离行为发生变化。

The aim of this study is to reveal the interaction relationships between lauryl dimethylamine N-oxide（LDAO） and peripheral light-harvesting complex（LH2） as well as the influence of LDAO on structure and function of LH2.In the present work,the effects of LDAO on the conformation and release processes of bacteriochlorophyll（BChl） of LH2 when incubated under different temperature and pH in the presence and absence of LDAO were investigated by spectroscopy.The results indicated that（1） the presence of LDAO resulted in alterations in the conformation,α-helix content,and spectra of Tyr and B850 band of LH2 at room temperature and pH 8.0.Moreover,energy transfer efficiency of LH2 was enhanced markedly in the presence of LDAO.（2） At 60 ℃,both the B800 and B850 band of LH2 were released and transited into free BChl at pH 8.0.However,the release rates of bacteriochlorophylls of B800 and B850 band from LH2 were slowed down and the release processes were changed when incubated in the presence of LDAO.Hence,the stability of LH2 was improved in the presence of LDAO.（3） The accelerated release processes of bacteriochlorophylls of B800 and B850 band of LH2 were induced to transform into bacteriopheophytin（BPhe） and free BChl by LDAO in strong acid and strong alkalic solution at room temperature.However,the kinetic patterns of the B800 and B850 band were remarkably different.The release and self-assemble processes of B850 in LH2 were observed in strong acid solution without LDAO.Therefore,the different release behaviors of B800 and B850 of LH2 are induced by LDAO under different extreme enviro nmental conditions.