Sun H W, Swope M, Cinquina C, Bedarkar S, Bernhagen J, Bucala R, Lolis E
Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06510, USA.
Protein Eng. 1996 Aug;9(8):631-5. doi: 10.1093/protein/9.8.631.
The subunit structure of human macrophage migration inhibitory factor (MIF) has been studied by preliminary X-ray analysis of wild-type and selenomethionine-MIF and dynamic light scattering. Crystal form I of MIF belongs to space group P2(1)2(1)2(1) and is grown from 2 M ammonium sulfate at pH 8.5. A native data set has been collected to 2.4 A resolution. Self-rotation studies and Van values indicate that three molecules per asymmetric unit are present. A data set to 2.8 A resolution has been collected for crystal form II, which belongs to space group P3(1)21 or P3(2)21 and grows from 2 M ammonium sulfate, 2% polyethylene glycol (average molecular mass 400) 0.1 M HEPES, pH 7.5. Three, four, five or six monomers in the asymmetric unit are consistent with Van values for this crystal form. Analysis of crystal form II containing selenomethionine-MIF indicates nine selenium sites are present per asymmetric unit. Dynamic light scattering of MIF suggests that the major form of the protein in solution is a trimer. The results of these studies are in contrast to previous reports indicating that MIF is a monomer or dimer. The subunit arrangement of MIF is similar to that of tumor necrosis factor and suggests that signal transduction might require trimerization of receptor subunits.
通过对野生型和硒代甲硫氨酸-MIF进行初步X射线分析以及动态光散射，对人巨噬细胞迁移抑制因子（MIF）的亚基结构进行了研究。MIF的晶型I属于空间群P2(1)2(1)2(1)，由pH 8.5的2 M硫酸铵生长而成。已收集到分辨率为2.4 Å的天然数据集。自旋转研究和Van值表明每个不对称单元存在三个分子。已收集到分辨率为2.8 Å的晶型II数据集，其属于空间群P3(1)21或P3(2)21，由2 M硫酸铵、2%聚乙二醇（平均分子量400）、0.1 M HEPES（pH 7.5）生长而成。不对称单元中的三个、四个、五个或六个单体与该晶型的Van值一致。对含有硒代甲硫氨酸-MIF的晶型II的分析表明每个不对称单元存在九个硒位点。MIF的动态光散射表明溶液中蛋白质的主要形式是三聚体。这些研究结果与之前表明MIF是单体或二聚体的报道相反。MIF的亚基排列与肿瘤坏死因子相似，表明信号转导可能需要受体亚基三聚化。
