The use of gene fusions to protein A and protein G in immunology and biotechnology.

This review describes the use of fusion proteins containing the immunoglobulin-binding domains of staphylococcal protein A (SpA) or the serum albumin-binding regions of streptococcal protein G (SpG), respectively, for various applications in immunology and biotechnology. The review will not cover the use of SpA and SpG for the purpose of immunoglobulin purification, but instead focus on other applications. Hundreds of SpA/SpG fusion proteins have been described in publications in the context of recombinant protein production, in a wide variety of host cells, with subsequent affinity purification of the gene product. However, this still constitutes just one area of their use. We will thus cover also other aspects of using SpA and SpG, including strategies to: (i) improve in vitro renaturation schemes for expressed gene products, (ii) enable affinity-assisted folding in vivo of target proteins, (iii) improve the stability to proteolysis of produced recombinant proteins, (iv) prolong the in vivo half-life of therapeutic proteins, (v) facilitate subunit vaccine development and functional cDNA analysis, (vi) select novel receptor variants with new specificities by the use of phage display technology.