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来源于Eisenia fetida的蚯蚓纤溶酶组分A,既是直接的纤溶酶,又是纤溶酶原激活物的蛋白质,已经被结晶.晶体属于正交晶系,空间群为P212121,每一个不对称单位含有3个蛋白质分子.为了解析该蛋白质的衍射相位,使用含有1.4 mol/L Li2SO4,0.1mol/L MOPS(pH 7.2)的重原子浸泡母液制备了4种合用的重原子衍生物.用差值Patterson法和差值Fourier法确定了衍生物晶体中重原子的位置,并将其联合修正获得0.25 nm分辨率的初始蛋白质结构相位.通过重原子位置关系确定了不对称单位中3个独立蛋白质分子之间的非晶体学对称关系,并利用其对初始的电子密度进行平均,大大提高了电子密度质量,为进一步的结构解析奠定了基础.
Fraxinus plasmin fraction A from Eisenia fetida, a protein that is both a direct plasmin and a plasminogen activator, has been crystallized. Crystals are orthorhombic and space group P212121, each not The symmetry unit contains 3 protein molecules. In order to analyze the diffraction phase of the protein, four kinds of combined heavy atom derivatives were prepared using a heavy atom soaking mother liquor containing 1.4 mol/L Li2SO4 and 0.1 mol/L MOPS (pH 7.2). Difference Patterson method and difference Fourier method determine the positions of heavy atoms in the derivative crystals, and jointly correct them to obtain the initial protein structure phase with 0.25 nm resolution. Three independent units in the asymmetry unit were determined by heavy atom position relationship. The non-crystallographic symmetry between protein molecules and the use of their average electron density have greatly improved the quality of electron density, laying the foundation for further structural analysis.