Bosch J, Tamura T, Bourenkov G, Baumeister W, Essen L O
Max-Planck-Institute of Biochemistry, Am Klopferspitz 18a, Martinsried bei München, D-82152, Germany.
J Struct Biol. 2001 Apr;134(1):83-7. doi: 10.1006/jsbi.2001.4360.
Tricorn protease from Thermoplasma acidophilum is a hexameric enzyme; in vivo the hexamers assemble further to form large icosahedral capsids of 14.6 MDa. Recombinant Tricorn protease was purified as an enzymatically active hexamer of 0.72 MDa that formed crystals of octahedral morphology under low-ionic-strength conditions. These crystals belong to space group C2 with unit cell dimensions a = 307.5 A, b = 163.2 A, c = 220.9 A, beta = 105.5 degrees and diffract to 2.2-A resolution using high-brilliance synchrotron radiation. Based on analysis of the self-rotation function and the presence of a pseudo-origin peak in the native Patterson map, a packing model was derived for the complex, comprising 1.5 hexamers per asymmetric unit with a solvent content of 43%. Due to the ninefold noncrystallographic symmetry the Tricorn crystals represent an interesting case for phasing X-ray crystallographic data by electron microscopic phase information.
嗜酸热原体的三角蛋白酶是一种六聚体酶；在体内，六聚体进一步组装形成14.6 MDa的大型二十面体衣壳。重组三角蛋白酶被纯化成为一种0.72 MDa的具有酶活性的六聚体，它在低离子强度条件下形成八面体形态的晶体。这些晶体属于空间群C2，晶胞参数为a = 307.5 Å，b = 163.2 Å，c = 220.9 Å，β = 105.5°，使用高亮度同步辐射可衍射至2.2 Å分辨率。基于对自旋转函数的分析以及在原生帕特森图中存在一个伪原点峰，推导出了该复合物的堆积模型，每个不对称单元包含1.5个六聚体，溶剂含量为43%。由于九重非晶体学对称性，三角蛋白酶晶体是通过电子显微镜相位信息对X射线晶体学数据进行相位分析的一个有趣案例。
