Aybay Cemalettin
Department of Immunology, Faculty of Medicine, Gazi University, 06500 Besevler, Ankara, Turkey.
Immunol Lett. 2003 Feb 3;85(3):231-5. doi: 10.1016/s0165-2478(02)00262-6.
It has been previously reported that staphylococcal protein A (SPA) bound only to the Fc region of mouse immunoglobulin G (IgG) and streptococcal protein G (SPG) bound to both Fab and Fc regions of mouse IgG and the binding sites for SPG and SPA on Fc were overlapped. In this study the binding characteristics of SPG and SPA for papain-digested mouse IgG were analysed. Papain digestion of mouse IgG purified from CAy-IFNg99C hybridoma (secreting IgG1 monoclonal antibody specific for human interferon gamma)-induced ascites resulted in Fab and two major Fc fragments referred to as the high molecular weight (HMW) and the low molecular weight (LMW) Fc fragments. SPG bound to Fab and the LMW Fc fragments of the papain-digested IgG. However SPG did not bind to the HMW Fc fragment. SPA showed practically no reactivity with the Fab and the LMW Fc fragments of the papain-digested mouse IgG but only to the HMW Fc fragment. SPG and SPA binding assays showed that papain digestion discriminated the SPG and SPA binding sites in the Fc fragment of mouse IgG. These results demonstrated a clear evidence for the presence of two independent SPG and SPA binding sites in the Fc fragment of mouse IgG.
先前已有报道称，葡萄球菌蛋白A（SPA）仅与小鼠免疫球蛋白G（IgG）的Fc区域结合，而链球菌蛋白G（SPG）与小鼠IgG的Fab和Fc区域均结合，且SPG和SPA在Fc上的结合位点相互重叠。在本研究中，分析了SPG和SPA对木瓜蛋白酶消化的小鼠IgG的结合特性。从CAy-IFNg99C杂交瘤（分泌针对人干扰素γ的IgG1单克隆抗体）诱导的腹水中纯化的小鼠IgG经木瓜蛋白酶消化后，产生了Fab以及两个主要的Fc片段，分别称为高分子量（HMW）和低分子量（LMW）Fc片段。SPG与木瓜蛋白酶消化的IgG的Fab和LMW Fc片段结合。然而，SPG不与HMW Fc片段结合。SPA与木瓜蛋白酶消化的小鼠IgG的Fab和LMW Fc片段几乎没有反应性，仅与HMW Fc片段结合。SPG和SPA结合试验表明，木瓜蛋白酶消化区分了小鼠IgG Fc片段中的SPG和SPA结合位点。这些结果清楚地证明了小鼠IgG Fc片段中存在两个独立的SPG和SPA结合位点。
