Gardner W D, Haselby J A, Hoch S O
J Immunol. 1980 Jun;124(6):2800-6.
One of the major proteins in human serum capable of binding DNA has been shown to be factor B of the alternative pathway of complement activation. This protein, designated DNA-binding protein-2 (DBP-2), is recognized by antisera directed against both factor B and its activated form, fragment Bb. Its m.w., charge microheterogeneity, and amino acid composition correspond closely with reported values for those properties of factor B. A radioimmunoassay was used to estimate the serum concentration of DBP-2 at 266 +/- 83 microgram/ml, which also corresponds with the level of factor B normally present in the serum. DBP-2 functions as factor B in the activation of factor B-depleted serum. Limited proteolytic treatment of DBP-2 produced a fragment pattern resembling that of factor B both in the m.w. of the fragments and their electrophoretic mobilities. By means of DNA affinity chromatography of the fragments produced by trypsinization, the DNA-binding domain of DBP-2 was localized.
人血清中能够结合DNA的一种主要蛋白质已被证明是补体激活替代途径的B因子。这种蛋白质被命名为DNA结合蛋白-2（DBP-2），它可被针对B因子及其活化形式Bb片段的抗血清识别。其分子量、电荷微不均一性和氨基酸组成与报道的B因子的这些特性值密切相符。采用放射免疫分析法估计DBP-2的血清浓度为266±83微克/毫升，这也与血清中正常存在的B因子水平相符。DBP-2在激活B因子缺陷血清中发挥B因子的作用。对DBP-2进行有限的蛋白水解处理，产生的片段模式在片段分子量及其电泳迁移率方面都类似于B因子。通过对胰蛋白酶消化产生的片段进行DNA亲和层析，确定了DBP-2的DNA结合结构域。
