Ce. Glatz et Cf. Ford, GENETIC-ENGINEERING TO ENHANCE THE SELECTIVITY OF PROTEIN SEPARATIONS, Applied biochemistry and biotechnology, 54(1-3), 1995, pp. 173-191
The ability to recover and purify natural and recombinant proteins, an
d the costs of doing so remain a major task in introducing the potenti
al products of biotechnology. The bases for separation range from spec
ific binding onto tailored reagents to solubility and partitioning beh
avior governed by a mixed bag of size, charge, and hydrophobicity. In
most cases, a combination of methods is used in sequence, and improvem
ents in the selectivity at an early stage can enhance the effectivenes
s of subsequent (and usually more costly) steps. Genetic engineering p
rovides a means of improving the selectivity within the context of exi
sting separation methods. By this strategy, improvements in selectivit
y are sought by bestowing a distinctive property on the protein of int
erest. The primary sequence of amino acids is altered, such that the p
rotein can be selectively removed from other components of the multico
mponent mixture in which such products are commonly found. In this art
icle, the range of these ''distinctive properties'' and their pairing
with various separation methods will be reviewed. Specific examples fr
om our work, in which a distinctive charge is provided via a polypepti
de ''purification'' fusion tail, will be discussed. Separation methods
we have used with these fusion proteins are precipitation, two-phase
aqueous extraction, reversed micellar extraction, and ion exchange usi
ng both resins and membranes.