Patent ID: 7193042

Claim:
A method for isolating an authentic, properly folded insulin-like growth factor (IGF) polypeptide from a medium into which the IGF polypeptide has been secreted by Pichia pastoris cells expressing the IGF polypeptide, wherein the method comprises: (a) performing a cation exchange chromatography with the medium to yield a first IGF mixture; (b) denaturing and renaturing IGF species present in the first IGF mixture 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 amount of authentic, properly folded IGF than the first IGF mixture, and further wherein only one cation exchange step is performed in the method.