Kihlberg B M, Sjöbring U, Kastern W, Björck L
Department of Medical and Physiological Chemistry, University of Lund, Sweden.
J Biol Chem. 1992 Dec 15;267(35):25583-8.
Immunoglobulin (Ig)-binding bacterial proteins have attracted theoretical interest for their role in molecular host-parasite interactions, and they are widely used as tools in immunology, biochemistry, medicine, and biotechnology. Protein L of the anaerobic bacterial species Peptostreptococcus magnus binds Ig light chains, whereas streptococcal protein G has affinity for the constant (Fc) region of IgG. In this report, Ig binding parts of protein L and protein G were combined to form a hybrid molecule, protein LG, which was found to bind a large majority of intact human Igs as well as Fc and Fab fragments, and Ig light chains. Binding to Ig was specific, and the affinity constants of the reactions between protein LG and human IgG, IgGFc fragments, and kappa light chains, determined by Scatchard plots, were 5.9 x 10(9), 2.2 x 10(9), and 2.0 x 10(9) M-1, respectively. The binding properties of protein LG were more complete as compared with previously described Ig-binding proteins when also tested against mouse and rat Igs. This hybrid protein thus represents a powerful tool for the binding, detection, and purification of antibodies and antibody fragments.
免疫球蛋白（Ig）结合细菌蛋白因其在分子宿主 - 寄生虫相互作用中的作用而引起了理论关注，并且它们在免疫学、生物化学、医学和生物技术中被广泛用作工具。厌氧细菌大消化链球菌的蛋白L结合Ig轻链，而链球菌蛋白G对IgG的恒定（Fc）区域具有亲和力。在本报告中，蛋白L和蛋白G的Ig结合部分被组合形成一个杂交分子，即蛋白LG，发现它能结合绝大多数完整的人Ig以及Fc和Fab片段，还有Ig轻链。与Ig的结合具有特异性，通过Scatchard图测定，蛋白LG与人IgG、IgG Fc片段和κ轻链之间反应的亲和常数分别为5.9×10⁹、2.2×10⁹和2.0×10⁹ M⁻¹。当也针对小鼠和大鼠Ig进行测试时，与先前描述的Ig结合蛋白相比，蛋白LG的结合特性更完善。因此，这种杂交蛋白是用于抗体和抗体片段的结合、检测及纯化的强大工具。
