Patent ID: 7071313

Claim:
A method for isolating an authentic, properly folded insulin-like growth factor (IGF) polypeptide from a medium into which an IGF polypeptide has been secreted by Saccharomyces cells expressing the IGF polypeptide, wherein the method comprises: (a) performing a first cation exchange chromatography with the Saccharomyces cell medium to yield a first IGF mixture; (b) denaturing and renaturing IGF species present in the first IGF mixture using a denaturation buffer comprising urea, dithiothreitol, alcohol, salt, and one or more divalent metals selected from the group consisting of Cu++, Mn++, Ni++, Zn++ and Fe++ in sufficient amounts and under conditions which allow for the reduction and subsequent oxidation of disulfide bonds, to yield a second IGF mixture; (c) subjecting the second IGF mixture to hydrophobic interaction chromatography to yield a third IGF mixture; and (d) performing reverse phase high performance liquid chromatography on the third IGF mixture to yield a fourth IGF mixture, wherein the fourth IGF mixture has a greater percentage of authentic, properly folded IGF than the first IGF mixture.