Toriumi Y, Park S Y, Hashimoto H, Shimizu H, Hirano M, Kamiya N
Toray Research Center Inc., 3-3-7 Sonoyama, Otsu, Shiga 520-8567, Japan.
Acta Crystallogr D Biol Crystallogr. 2001 Sep;57(Pt 9):1326-8. doi: 10.1107/s0907444901011969. Epub 2001 Aug 23.
The crystallization and preliminary crystallographic study of phycocyanin from the thermophilic cyanobacterium Synechococcus elongatus is reported. Phycocyanin is composed of alpha- and beta-subunits consisting of 162 and 172 amino-acid residues, respectively. These associate to form an alphabeta heterodimer, which further associates to give a ring-shaped trimer (alphabeta)(3). Two trimers bind head-to-head to form a hexamer (alphabeta)(6). Phycocyanin crystals have been obtained by the sitting-drop vapour-diffusion method with a precipitant solution containing 30%(w/v) PEG 4000 and 100 mM MES pH 7.5-8.0. Using synchrotron radiation, the crystals diffract to 2.0 A resolution. They belong to the trigonal space group R32, with unit-cell parameters a = b = 186.75 (3), c = 59.75 (4) A, alpha = beta = 90, gamma = 120 degrees. Assuming that the crystallographic triad is identical to the threefold axis of the hexamer and with three (alphabeta)(6) molecules in a unit cell, the calculated molar volume (V(M)) is 2.64 A(3) Da(-1). This value corresponds to a solvent content of approximately 53%, with one alphabeta heterodimer occupying the asymmetric unit.
报道了嗜热蓝藻细长聚球藻藻蓝蛋白的结晶及初步晶体学研究。藻蓝蛋白由α亚基和β亚基组成，分别含有162个和172个氨基酸残基。这些亚基缔合形成αβ异二聚体，αβ异二聚体进一步缔合形成环状三聚体(αβ)₃。两个三聚体头对头结合形成六聚体(αβ)₆。采用坐滴气相扩散法，以含有30%（w/v）聚乙二醇4000和100 mM MES（pH 7.5 - 8.0）的沉淀剂溶液获得了藻蓝蛋白晶体。利用同步辐射，这些晶体的衍射分辨率达到2.0 Å。它们属于三方晶系R32空间群，晶胞参数a = b = 186.75 (3) Å，c = 59.75 (4) Å，α = β = 90°，γ = 120°。假设晶体学三重轴与六聚体的三重轴相同，且一个晶胞中有三个(αβ)₆分子，则计算得到的摩尔体积（V(M)）为2.64 ų Da⁻¹。该值对应于约53%的溶剂含量，一个αβ异二聚体占据不对称单元。
