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首页> 外文期刊>Biochemistry >A structural Investigation of the Central Chlorophy a Binding Sites in the Minor Photosystem II Antenna Protein, Lhcb4
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A structural Investigation of the Central Chlorophy a Binding Sites in the Minor Photosystem II Antenna Protein, Lhcb4

机译：在次要光系统II天线蛋白Lhcb4中中央叶绿素a结合位点的结构研究。

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Mutant proteins from light-harvesting complexes of higher plants may be obtained by expressing modified apoproteins in Escherichia coli, and reconstituting them in the presence of chlorophyll and carotenoid cofactors. This method has allowed, in particular, the engineering of mutant LHCs in which each of the residues coordinating the central Mg atoms of the chlorophylls was replaced by noncoordinating amino acids [Bassi, R., Croce, R., Cugini, D., and Sandona, D.(1999) Proc. Natl. Acad. Sci. U.S.A. 96, 10056-10061]. The vailability of these mutants is of particular importance for determining the precise position of absorption bands for the different chlorophyll molecules, as well as the sequence of energy transfer events that occur within LHC complexes, provided that the structural impact of each mutation is precisely evaluated. Using resonance Raman spectroscopy, we have characterized the pigment-protein interactions in the minor photosystem II antenna protein, Lhcb4 (CP29), in which each of three of the four central chlorophyll a molecules has been removed by such mutations. By comparing the spectra of these mutants with those of wild-type protein, the state of interaction of the carbonyl group, the coordination state of the central magnesium ion, and the dielectric constant (polarity) of the limmediate environment in the binding pocket of the chlorophyll a molecule were defined for each cofactor binding site. In addition, the structural impact of the absence of one chlorophyll a molecule and the quality of protein folding were evaluated for each of these mutated polypeptides.
机译：可以通过在大肠杆菌中表达修饰的载脂蛋白，并在叶绿素和类胡萝卜素辅因子的存在下对其进行重组来获得来自高等植物光采复合物的突变蛋白。该方法尤其允许突变LHC的工程改造，其中配位于叶绿素中心Mg原子的每个残基均被非配位氨基酸取代[Bassi，R.，Croce，R.，Cugini，D.，and桑多纳（1999） Natl。学院科学U.S.A. 96，10056-10061]。这些突变体的有效性对于确定不同叶绿素分子的吸收带的精确位置以及LHC复合物中发生的能量转移事件的顺序特别重要，前提是必须精确评估每个突变的结构影响。使用共振拉曼光谱，我们表征了次要光系统II天线蛋白Lhcb4（CP29）中的色素-蛋白质相互作用，其中四个中央叶绿素a分子中的三个已被此类突变去除。通过比较这些突变体与野生型蛋白的光谱，羰基的相互作用状态，中心镁离子的配位状态以及高能环境的介电常数（极性）在其结合袋中。为每个辅因子结合位点定义了叶绿素a分子。另外，对于这些突变的多肽中的每一个，评估了不存在一个叶绿素a分子的结构影响和蛋白质折叠的质量。

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