Here's how PEC deploys "directed" or "forced" evolution, tomake systematic changes in the amino acid sequence of anexisting protein, potentially producing millions of variants:
First, it achieves genetic variation through controlled, random,mixed-base mutagenesis of DNA, yielding a mixture of nucleicacid molecules encoding different but related potential bindingproteins.
Second, to select mutated genes encoding novel proteins withdesirable binding properties, it inserts the genes into a libraryof phages; these display the variegated proteins on their virionsurface.
Third, it screens for the optimum protein by exposing the viralmixture to immobilized targets and amplifies the proteinsshowing maximum binding affinity.
Fourth, it inserts the preferred binding-protein gene into yeasthost cells to reproduce the protein of interest.
"One virtue of the proteins we are engineering," said JohnFreeman, company chairman and CEO, "is that they don'trequire expression in mammalian cells. They are small andnon-glycosylated, which makes them easier and less expensiveto express and produce in yeast and bacterial hosts."
Scientific director Robert Ladner added, "We think this is ageneral method for making protease inhibitors with very highspecificity and affinity." -- David N. Leff
(c) 1997 American Health Consultants. All rights reserved.