Quiocho F A, Reeke G N, Becker J W, Lipscomb W N, Edelman G M
Proc Natl Acad Sci U S A. 1971 Aug;68(8):1853-7. doi: 10.1073/pnas.68.8.1853.
Concanavalin A, a phytohemagglutinin isolated from the jack bean, crystallizes at pH 6.8 in the orthorhombic space group 1222 with a = 89.9, b = 87.2, and c = 63.1 A. We have analyzed x-ray diffraction intensity data to 4 A resolution on native concanavalin A and five heavy-metal derivatives: lead, mersalyl, chloroplatinate, uranyl, and o-mercuri-p-nitrophenol. Heavy-atom positions, occupancies, and isotropic thermal parameters have been refined by least-squares methods. The electron density maps clearly show the molecular shape and the packing of the concanavalin A molecules. The asymmetric unit (mol wt 27,000) forms an elliptical dome or "gumdrop" with a base of approximately 46 x 26 A and a height of 42 A. The subunits are paired across 2-fold axes parallel to the c-axis to form dimers. The dimers are in turn paired across points of D(2) symmetry to form tetramers of roughly tetrahedral shape. Each unit has a depression located on the surface which could be the site of saccharide binding. In many regions we have been able to trace the course of the polypeptide chain.
伴刀豆球蛋白A是一种从刀豆中分离出的植物血凝素，在pH 6.8时结晶，属于正交晶系空间群P222，a = 89.9，b = 87.2，c = 63.1埃。我们已经分析了天然伴刀豆球蛋白A以及五种重金属衍生物（铅、汞撒利、氯铂酸盐、铀酰和邻 - 汞 - 对硝基苯酚）至4埃分辨率的X射线衍射强度数据。通过最小二乘法对重原子位置、占有率和各向同性热参数进行了精修。电子密度图清晰地显示了伴刀豆球蛋白A分子的形状和堆积方式。不对称单元（分子量27,000）形成一个椭圆形穹顶或“软糖”状，底部约为46×26埃，高度为42埃。亚基通过平行于c轴的二次轴配对形成二聚体。二聚体又通过D(2)对称点配对形成大致呈四面体形状的四聚体。每个单元在表面有一个凹陷，可能是糖类结合的位点。在许多区域我们已经能够追踪多肽链的走向。
