Streptococcal Fc receptor proteins. Application for biotechnology

 On the basis of a polyfunctional G-protein receptor of the group G streptococcus biotechnological reagents were created as monofunctional recombinant polypeptides for the separate binding of immunoglobulin G or human serum albumin (defended by patents of Russia). Receptor proteins and their ligands are used for an analysis of multicenter "protein-protein" interaction and for the development of a new analytical approach — a receptor-enzyme analysis — an analogue of the immune-enzyme analysis in which the antibodies to IgG and albumin are substituted by receptor peptides that increased the specificity of the reactions and made them simpler. The albumin test proved to be highly informative for screening microalbuminuria in diabetes patients and for preclinical diagnosing diabetic nephropathy — a heavy complication of a fairly spread disease of people.

 The method of highly effective monolithic chromatography was used to determine the parameters of affine interaction of recombinant forms of the G-protein receptor with main blood proteins of man: immunoglobulin G and albumin. The reaction was highly specific and each pair "ligand-receptor" was formed as a minimum at the expense of two centres of binding. A method of rapid isolation of highly purified albumin and immunoglobulin was developed and a scheme of plasma fractionation is proposed with a synchronous extraction of the both proteins.

 For the improvement of the developed receptor-enzymatic analysis in which a specific receptor protein was used instead of antibodies model systems were made for a comparison of the binding capacity of two prototypes of microchip (nitrocellulose membrane and macropore monolithic polymer). Both systems were tested for revealing microalbuminuria (the reagents were serum albumin of man and specific receptor protein from the group G streptococcus) as a criterion for revealing diabetic nephropathy in diabetes patients.