Isolation of a specific albumin receptor from a group G streptococcal strain

The albumin receptor, a bacterial cell-wall protein with affinity for albumin, has been isolated from a bovine group G streptococcal strain (DG-8). Bacterial surface proteins were solubilized by boiling in 0.6M HCl for 5 min. The albumin receptor was isolated by sequential use of ion-exchange chromatography on DEAE-Sephadex A-50 and affinity chromatography on albumin coupled Sepharose 4B. The presence of albumin receptor in various pools and fractions during the isolation was followed by their ability to inhibit the binding of radiolabelled albumin to DG-8 bacteria. A highly purified albumin receptor was obtained according to Western blot analysis. The albumin binding band obtained showed a molecular weight of about 30,000. The purified receptor did not possess any IgG binding capacity. 50 micrograms albumin receptor was prepared from each gram of bacteria.