ABSTRACT
This chapter will describe how genetic approaches can be used to simplify recovery of recombinant proteins. Gene fusion technology resulting in the expression of fusion proteins, having the combined properties of the parental gene products, has found widespread use in biotechnology. Applications of fusion proteins include facilitated purification of the target protein; means to decrease proteolysis of the target protein; display of proteins on surfaces of cells, phages, or viruses; construction of reporter molecules for the monitoring of gene expression and protein localization; and strategies to increase the circulation half-life of protein therapeutics. However, as pioneered by Uhlén and coworkers (1983), the most common application of gene fusions has been for the purpose of affinity purification of recombinant proteins. Recently, gene technology in the format of combinatorial protein engineering has allowed in vitro selection of novel proteins that selectively bind a desired target molecule. This new emerging technology enables the de novo creation of purpose-designed ligands suitable for affinity chromatography applications. A general overview of commonly used affinity tags will be followed by some examples of specific applications for affinity tags and a description of some novel trends in how genetic approaches can be employed to facilitate purification.
