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  • Purification and some properties of streptococcal protein G, a novel IgG-binding reagent.

Purification and some properties of streptococcal protein G, a novel IgG-binding reagent.

Journal of immunology (Baltimore, Md. : 1950) (1984-08-01)
L Björck, G Kronvall
摘要

Protein G, a bacterial cell wall protein with affinity for immunoglobulin G (IgG), has been isolated from a human group G streptococcal strain (G148). Bacterial surface proteins were solubilized by enzymatic digestion with papain. Protein G was isolated by sequential use of ion-exchange chromatography on DEAE-cellulose, gel filtration on Sephadex G-100, and affinity chromatography on Sepharose 4B-coupled IgG. The presence of protein G in various pools and fractions during the isolation was followed by their ability to inhibit the binding of radio-labeled IgG to G148 bacteria. A highly purified protein G was obtained. On polyacrylamide gel electrophoresis in sodium dodecyl sulfate, the apparent m.w. was 30,000, and on agarose gel electrophoresis the purified protein gave rise to a single band in the alpha 1-region. Protein G was found to bind all human IgG subclasses and also rabbit, mouse, and goat IgG. On the IgG molecule, the Fc part appears mainly responsible for the interaction with protein G, although a low degree interaction was also recorded for Fab fragments. IgM, IgA, and IgD, however, showed no binding to protein G. This novel IgG-binding reagent promises to be of theoretical and practical interest in immunologic research.

材料
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Roche
蛋白G琼脂糖, >98% (HPLC and SDS-PAGE), suspension
Millipore
蛋白G琼脂糖凝胶®,快速流动, recombinant, expressed in E. coli, aqueous ethanol suspension
Sigma-Aldrich
Protein G, Recombinant, E. coli