McPherson A, Brayer G, Cascio D, Williams R
Science. 1986 May 9;232(4751):765-8. doi: 10.1126/science.3961503.
The crystalline complex of pancreatic ribonuclease (RNase) with oligomers of d(pA)4 has been solved by x-ray diffraction methods and refined by standard procedures to a conventional crystallographic R factor of 0.22 at 2.5 angstrom resolution. The asymmetric unit is a complex of one RNase molecule associated with four d(pA)4 oligomers. Although the DNA in this complex is segmented, and therefore shows some discontinuities, it nevertheless traces a continuous path 12 nucleotides in length that passes through the active site cleft of the enzyme and over the surface of the protein. The DNA makes a series of eight to nine electrostatic bonds between its phosphate groups and lysine and arginine residues on the protein, as well as specific chemical interactions at the active site. The path described by the sequence of nucleotides is likely to be that taken by an extended polynucleotide chain when it is bound by the enzyme.
通过X射线衍射方法解析了胰腺核糖核酸酶（RNase）与d(pA)4寡聚物的晶体复合物，并采用标准程序将其精修至2.5埃分辨率下传统晶体学R因子为0.22。不对称单元是一个由一个RNase分子与四个d(pA)4寡聚物组成的复合物。尽管该复合物中的DNA是分段的，因此存在一些不连续性，但它仍然描绘出一条长度为12个核苷酸的连续路径，该路径穿过酶的活性位点裂隙并覆盖在蛋白质表面。DNA在其磷酸基团与蛋白质上的赖氨酸和精氨酸残基之间形成了一系列八到九个静电键，以及在活性位点处的特定化学相互作用。核苷酸序列所描述的路径很可能是延伸的多核苷酸链被该酶结合时所采取的路径。
