Ljungberg U K, Jansson B, Niss U, Nilsson R, Sandberg B E, Nilsson B
Department of Immunology, Excorim AB, Lund, Sweden.
Mol Immunol. 1993 Oct;30(14):1279-85. doi: 10.1016/0161-5890(93)90044-c.
Binding properties of staphylococcal protein A (SpA) to different human immunoglobulins have been investigated. In this analysis, intact SpA as well as SpA-derived fragments containing one to five IgG-binding domains of different compositions, were used. The affinity binding constants of the different proteins to human polyclonal IgG, IgA, IgM and F(ab')2-fragments as well as their binding capacity to the immunoglobulin molecules were determined. The results show that although all the proteins bound to IgG, regardless of size or composition, the binding strength differed significantly. Proteins containing five domains have a stronger affinity for IgG than those containing one or two. There were no marked differences in binding strength between different domains. However, the binding ability to IgA and IgM showed a marked difference between the various SpA-derived proteins of different compositions. This discrepancy was correlated to differences in their relative binding properties to isolated F(ab')2-fragments of IgG. Hence, we conclude that the binding affinity is mainly affected by the number of domains, whereas the binding specificity is to a large extent determined by which domains are selected.
已对葡萄球菌蛋白A（SpA）与不同人类免疫球蛋白的结合特性进行了研究。在该分析中，使用了完整的SpA以及含有一至五个不同组成的IgG结合结构域的SpA衍生片段。测定了不同蛋白质与人多克隆IgG、IgA、IgM和F(ab')2片段的亲和结合常数以及它们与免疫球蛋白分子的结合能力。结果表明，尽管所有蛋白质均与IgG结合，无论其大小或组成如何，但其结合强度存在显著差异。含有五个结构域的蛋白质对IgG的亲和力比含有一个或两个结构域的蛋白质更强。不同结构域之间的结合强度没有明显差异。然而，不同组成的各种SpA衍生蛋白质对IgA和IgM的结合能力存在显著差异。这种差异与它们对分离的IgG F(ab')2片段的相对结合特性差异相关。因此，我们得出结论，结合亲和力主要受结构域数量的影响，而结合特异性在很大程度上取决于所选择的结构域。
