CHLOROPHYLL-PROTEIN COMPLEXES OF BARLEY PHOTOSYSTEM-I
CHLOROPHYLL-PROTEIN COMPLEXES OF BARLEY PHOTOSYSTEM-I
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DOI：
10.1111/j.1432-1033.1987.tb10791.x
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发表时间：
1987-03-02
期刊：
影响因子：
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通讯作者：
SIMPSON, D
中科院分区：
文献类型：
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作者：
BASSI, R;SIMPSON, D
用两种不同的方法从大麦类囊体中分离出叶绿素a/B比为6.0的光系统I（PSI）制剂。通过非变性凝胶电泳解析的高分子量复合物（CP 1a *）具有与通过Triton X-100溶解类囊体然后通过蔗糖梯度超离心分离的PSI制备物（PSI-200）相同的性质。该材料的叶绿素：P700比为208：1，由三种不同的叶绿素-蛋白质复合物组成，它们可以通过将PSI制剂溶解在十二烷基麦芽糖苷中，然后进行蔗糖梯度超离心而彼此分离。大约一半的叶绿素，包括所有的叶绿素B，位于两个天线复合体命名为LHCI-680和LHCI-730，这是通过其特征的低温荧光发射光谱。其余的叶绿素a与PSI反应中心P700 Chla-P1相关，其在720 nm处发出荧光。每个叶绿素-蛋白质复合物具有独特的多肽组成和特征圆二色性和吸收光谱。使用十二烷基麦芽糖苷代替十二烷基硫酸盐导致LHCI-680的较少变性形式，其在77 K下在690 nm处发荧光。其中一个蔗糖梯度部分含有仅由LHCI-730和P700 Chla-P1组成的复合物，该复合物在731 nm处发出荧光，表明LHCI-730在结构上与P700 Chla-P1相关并猝灭其荧光。大约四分之三的捕光天线叶绿素在LHCI-730中，但只需要大约四分之一的LHCI-730正常补体来淬灭反应中心。通过相对于叶绿素浓度减少Triton的量，分离出叶绿素a/B比为3.5的PSI制剂，其中叶绿素：P700比为300：1。它不含光系统II，但含有大量与PSI反应中心功能相关的LHCII。重构研究表明，从LHCII到PSI的激发能转移需要LHCI-680的存在，并且我们提出，在PSI中，发生以下线性激发能转移序列：LHCI-680 →LHCI-730 →P700 Chla-P1。
Photosystem I (PSI) preparations with a chlorophyll a/b ratio of 6.0 were isolated from barley thylakoids using two different methods. The high-molecular-mass complex (CP1a*) which is resolved by non-denaturing gel electrophoresis had the same properties as a PSI preparation (PSI-200) isolated by Triton X-100 solubilisation of thylakoids followed by sucrose gradient ultracentrifugation. This material had a chlorophyll:P700 ratio of 208:1 and was composed of three different chlorophyll-protein complexes which could be separated from each other by solubilising the PSI preparation in dodecyl maltoside followed by sucrose gradient ultracentrifugation. Approximately half of the chlorophyll, including all the chlorophyll b, was located in two antenna complexes designated LHCI-680 and LHCI-730, which were identified by their characteristic low-temperature fluorescence emission spectra. The rest of the chlorophyll a was associated with the PSI reaction centre, P700 Chla-P1, which fluoresced at 720 nm. Each chlorophyll-protein complex had a unique polypeptide composition and characteristic circular dichroic and absorption spectra. The use of dodecyl maltoside instead of dodecyl sulphate resulted in a less denatured form of LHCI-680, which fluoresced at 690 nm at 77 K. One of the sucrose gradient fractions contained a complex consisting of only LHCI-730 and P700 Chla-P1 which fluoresced at 731 nm, indicated that LHCI-730 is structurally associated with P700 Chla-P1 and quenches its fluorescence. Approximately three-quarters of the light-harvesting antenna chlorophyll was in LHCI-730, but only about one-quarter of the normal complement of LHCI-730 was required to quench the reaction centre. By reducing the amount of Triton relative to the chlorophyll concentration, a PSI preparation chlorophyll a/b ratio of 3.5) with a chlorophyll:P700 ratio of 300:1 was isolated. It contained no photosystem II, but a significant amount of LHCII which was functionally connected to the PSI reaction centre. Reconstitution studies demonstrated that excitation energy transfer from LHCII to PSI requires the presence of LHCI-680, and we propose that, in PSI, the following linear excitation energy transfer sequence occurs: LHCII .fwdarw. LHCI-680 .fwdarw. LHCI-730 .fwdarw. P700 Chla-P1.