Hakoshima T, Tomita K
Faculty of Pharmaceutical Sciences, Osaka University, Japan.
J Mol Biol. 1988 May 20;201(2):455-7. doi: 10.1016/0022-2836(88)90153-2.
Crystals of recombinant human tumor necrosis factor produced by Escherichia coli have been obtained under different conditions. Crystals suitable for X-ray studies are produced by a vapor diffusion technique using sodium phosphate as both precipitant and buffer at pH 6.5. The crystals belong to the cubic space group, P2(1)3 with unit cell dimensions a = b = c = 95.7 A (1 A = 0.1 nm). Preliminary photography reveals that the crystals are moderately stable to X-rays and diffract to at least 3 A resolution. The diffraction data for native crystals have been collected on a diffractometer at 3 A resolution. Another crystal form, which appeared in a solution containing sodium phosphate at pH 8.0, has the trigonal space group P3 with unit cell dimensions a = b = 63.8 A and c = 54.4 A, and produces measurable reflections to a resolution of 3 A. Hexagonal crystals also have been obtained by the use of polyethylene glycol as precipitant in the range pH 7.6 to 8.0; however, the crystals are fragile and unstable to X-rays. Conservation of 3-fold symmetry in the different crystal forms obtained could reflect the ability of tumor necrosis factor molecules to form trimers in solution and probably the nature of binding of the molecules to cellular receptors.
在不同条件下已获得由大肠杆菌产生的重组人肿瘤坏死因子晶体。适合进行X射线研究的晶体是通过气相扩散技术制备的，该技术使用磷酸钠作为沉淀剂和pH 6.5的缓冲剂。这些晶体属于立方空间群P2(1)3，晶胞参数a = b = c = 95.7 Å（1 Å = 0.1 nm）。初步摄影显示，这些晶体对X射线具有中等稳定性，并且至少能衍射到3 Å分辨率。天然晶体的衍射数据已在衍射仪上以3 Å分辨率收集。另一种晶体形式出现在pH 8.0的含磷酸钠溶液中，属于三方空间群P3，晶胞参数a = b = 63.8 Å，c = 54.4 Å，并且能产生分辨率为3 Å的可测量反射。通过在pH 7.6至8.0范围内使用聚乙二醇作为沉淀剂也获得了六方晶体；然而，这些晶体易碎且对X射线不稳定。在获得的不同晶体形式中保持三重对称性可能反映了肿瘤坏死因子分子在溶液中形成三聚体的能力，以及分子与细胞受体结合的性质。
