Structural role of lipids in molecular architecture of photosystem I in thylakoid membranes.

从菠菜类囊体中分离得到叶绿素-蛋白质复合体。这些复合体分别命名为CPI‘(反应中心富集光系统I)和LHCI(与光系统I相关的捕光Chla/b蛋白复合体)。当CPI‘与LHCI重组为大豆磷脂酰胆碱(PC)脂质体时，在光限制条件下蛋白质脂质体中P700-光氧化的一级速率常数(KP700)约为未重组为脂质体的两个络合物混合物的两倍。重组为大豆PC的两种络合物的蛋白脂质体的荧光发射光谱(77K)在730-733 nm处有一个较长的波长带，这在没有脂质体的CPI‘和LHCI的混合物中没有消失。圆二色谱表明，两种络合物重组成大豆PC后，665 nm处的正峰和686 nm处的负峰的强度都有所增加。I…为了进一步研究与类囊体脂重组是否会影响kP700，用LHCI将CPI‘重组为菠菜类囊体脂质体。用酸性脂类(由磺基喹诺酮二酰甘油和磷脂酰甘油组成)重建对kP700无影响。另一方面，当CPI‘和LHCI的混合物被重组为中性脂质时，其kP700显著增加。事实上，与单半乳糖二酰甘油(含20%(W/W)大豆PC制成脂质体)重组后，在两种不含脂质体的混合物中，kP700以上的刺激率为75%，而双半乳糖二酰甘油(含20%大豆PC)的刺激率约为30%。这些结果表明，在由CPI‘和LHCI重组的蛋白脂质体中，叶绿素的组织发生了一些变化，促进了从LHCI到光系统I的反应中心的能量转移，单半乳糖二酰甘油酯在与光系统I相关的叶绿素-蛋白质复合体进入类囊体膜的双层中起着重要的作用。较少

Chlorophyll-protein complexes were isolated from spinach thylakoids. These complexes were designated CPI' (reaction-center enriched photosystem I), and LHCI (light-harvesting Chl a/b-protein complex associated with photosystem I). When CPI' was reconstituted with LHCI into liposomes of soybean phosphatidylcholine (PC), the first-order rate constant for P700-photooxidation (kP700) in proteoliposomes under light-limiting conditions was approximately double that of a mixture of two complexes not reconstituted into liposomes. The fluorescence emission spectrum (77 K) of the proteoliposomes of the two complexes reconstituted into soybean PC displayed a longer wavelength band at 730-733 nm which was not dispalyed in the spectrum of a mixture of CPI' and LHCI without liposomes. The circular dichroism spectrum of the two complexes indicated that the intensities of both a positive peak at 665 nm and a negative peak at 686 nm increased when the two complexes were reconstituted into soybean PC. I … More n order to investigate whether reconstitution with thylakoid lipids would affect kP700, CPI' was reconstituted with LHCI into liposomes of lipids isolated from spinach thylakoids. Reconstitution with acidic lipids (consisted of sulfoquinovosyldiacylglycerol and phosphatidylglycerol) resulted in no effect on kP700. On the other hand, kP700 of a mixture of CPI' and LHCI increased significantly when the two complexes were reconstituted into neutral lipids. In fact reconstitution with monogalactosyldiacylglycerol (containing 20%(W/W) soybean PC for making liposomes) gave a 75% stimulation above kP700 in a mixture of the two complexes without liposomes, and digalactosyldiacylglycerol (containing 20% soybean PC) gave about 30% stimulation. These results results suggest that some alteration of chlorophyll organization occurs in proteoliposomes reconstituted with both CPI' and LHCI, facilitating energy transfer from LHCI to the reaction center of photosystem I, and monogalactosyldiacylglyceride plays an important role in the incorporation of chlorophyll-protein complexes associated with photosystem I into the bilayer of the thylakoid membranes. Less