ENGINEERED BACTERIAL FC RECEPTORS

Five new-type FC receptor molecules were constructed based on streptoc occal protein G (SpG) and staphylococcal protein A (SpA). These protei n molecules contain one to six Fc binding domains to immunoglobulins w hich are structurally different from native SpG or SpA. Their expressi on levels reached 17-30% of the total bacterial proteins after heat in duction in E. coli. Immunodiffusion and ELISA results showed that the engineered protein TG (184 amino acid residues) composed of three SpG C3 domain could bind more broadly and efficiently than the native SpG to the IgGs of human, goat, rabbit, etc., and its optimal pH for bindi ng became wider (pH5-8) compared with the SpG (pH5); and the protein T GA (357AA), fused by protein TG and the A, B, C domains of SpA, displa yed both the binding pattern of SpG and SpA.