Advances in molecular biology have provided researchers with the opportunity to develop increasingly rational approaches to the design of therapeutic drugs. This technology, when used with computer-assisted molecular modeling, is called protein engineering.
Protein engineering combines many techniques, including gene cloning, site-directed mutagenesis, protein expression, structural characterization of the product, and bioactivity analyses; it can be used to modify the primary sequence of a protein at selected sites to improve stability, pharmacokinetics, bioactivity, and serum half-life. A second application of protein engineering is the design of hybrid proteins that contain regions that aid separation and purification. That is achieved by introducing, next to the structural gene for the desired product, a DNA sequence that encodes for a specific polypeptide "tail."
The tails can be inserted at the N or C terminal of the protein to yield a fusion protein with special properties that facilitate separation. Such genetic modifications can be designed to take advantage of affinity, ion-exchange, hydrophobic, metal chelate, and covalent separations. The special properties of fusion proteins allow crude microbial extracts to be passed over an adsorbent that binds specifically to the tail, so that the desired product is retained and contaminants pass through. After elution and treatment to remove the tail, the product is purified further by standard methods, such as size-exclusion chromatography or high-performance liquid chromatography (HPLC).
Tags: Bio Technology, Bio Genetics, Bio Process Engineering
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