Affinity chromatography of RNase inhibitor

Of the reagents used in reverse transcription-PCR (RT-PCR), RNase Inhibitor is the most costly on a per assay basis. A simple method for purification of RNase Inhibitor from bovine liver is described. Approximately 40,000 units of RNase Inhibitor can be purified to homogeneity from 400 g of bovine liver within two days using inexpensive reagents. The method described employs (a) facile procedures to rapidly obtain a clarified liver extract, (b) affinity chromatography of RNase Inhibitor on RNase-A-Sepharose, and (c) batchwise concentration of the purified protein with a molecular sieve resin.