Crystal structure of allophycocyanin from red algae Porphyra yezoensis at 2.2-Å resolution
Crystal structure of allophycocyanin from red algae Porphyra yezoensis at 2.2-Å resolution
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DOI：
10.1074/jbc.274.24.16945
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发表时间：
1999-06-11
影响因子：
4.8
通讯作者：
Liang, DC
中科院分区：
文献类型：
--
作者：
Liu, JY;Jiang, T;Liang, DC
采用分子置换法测定了条斑紫菜（Porphyra yezoensis）别藻蓝蛋白（APC - PY）2.2埃分辨率的晶体结构。该晶体属于R32空间群，晶胞参数为a = b = 105.3埃，c = 189.4埃，α = β = 90°，γ = 120°。利用X - PLOR程序进行多次精修，并根据电子密度图构建模型后，在10.0 - 2.2埃范围内，晶体学R因子收敛至19.3%（自由R因子为26.9%）。键长和键角的均方根偏差分别为0.015埃和2.9°。在晶体中，两个APC - PY三聚体面对面结合形成一个六聚体。六聚体中两个三聚体的组装方式与C - 藻蓝蛋白（C - PC）和R - 藻红蛋白（R - PE）六聚体相似，但两个三聚体与六聚体的组装紧密程度不如C - PC和R - PE六聚体。讨论了生色团 - 蛋白质相互作用以及可能的能量传递途径。APC - PY的藻蓝胆素1α84与另一个单体的2β亚基中的3个残基形成5个氢键。在R - PE和C - PC中，生色团1α84仅与2β亚基中的2β77残基形成1个氢键。这一结果可能支持并解释APC三聚体和单体之间存在的较大光谱差异。
The crystal structure of allophycocyanin from red algae Porphyra yezoensis (APC-PY) at 2.2-Angstrom resolution has been determined by the molecular replacement method. The crystal belongs to space group R32 with cell parameters a = b = 105.3 Angstrom, c = 189.4 Angstrom, alpha = beta = 90 degrees, gamma = 120 degrees, After several cycles of refinement using program X-PLOR and model building based on the electron density map, the crystallographic R-factor converged to 19.3% (R-free factor is 26.9%) in the range of 10.0 to 2.2 Angstrom The r.m.s. deviations of bond length and angles are 0.015 Angstrom and 2.9 degrees, respectively.In the crystal, two APC-PY trimers associate face to face into a hexamer, The assembly of two trimers within the hexamer is similar to that of C-phycocyanin (C-PC) and R-phycoerythrin (R-PE) hexamers, but the assembly tightness of the two trimers to the hexamer is not so high as that in C-PC and R-PE hexamers,The chromophore-protein interactions and possible pathway of energy transfer were discussed. Phycocyanobilin 1 alpha 84 of APC-PY forms 5 hydrogen bonds with 3 residues in subunit 2 beta of another monomer, In R-PE and C-PC, chromophore 1 alpha 84 only forms 1 hydrogen bond with 2 beta 77 residue in subunit 2 beta. This result may support and explain great spectrum difference exists between APC trimer and monomer.