Construction, expression, functional сharacterization and practical application of fusion protein SPA-ВAPmut

Aim. The creation of genetically engineered fusion protein SPA-BAPmut and its application as a secondary immunoreagent in immunoassays. Methods. Gene cloning, PCR, electrophoresis, DNA sequencing, bacteria cells culturing, protein expression and purification, ELISA, Western-blotting were used. Results. The DNA sequences encoding Staphylococcus aureus protein A (SPA) and bacterial alkaline phosphatase with enhanced catalytic activity (BAPmut) were used for construction of gene encoding fusion protein SPA-BAPmut that was expressed in the high-productive Escherichia coli system and obtained in a soluble form. Cultivation conditions to provide a high-level expression of SPA-ВAPmut (> 1 g/l) were determined. The target protein was obtained with purity more than 95 % using МАХ method. SPA-ВAPmut is thermostable, and both parts of fusion protein (SPA and BAPmut) retain their IgG binding and alkaline phosphatase activity for a long time. SPA-BAPmut was used as a substitute of secondary antibodies in immunoassays. As little as 5 ng of the antigen could be detected in Western blotting and 1 g/ml of IgG in ELISA. Conclusions. The possibility of using SPA-ВAPmut as universal secondary immunoreagent for different types of immunoassays was shown.