Preparation of soluble proteins from Escherichia coli

Purification of human IL-1beta is used in this unit as an example of the preparation of soluble proteins from E. coli. Bacteria containing IL-1beta are lysed, and IL-1 beta in the resulting supernatant is purified by anion-exchange chromatography, salt precipitation and cation-exchange chromatography, and then concentrated. Finally, the IL-1 beta protein is applied to a gel-filtration column to separate it from remaining higher- and lower-molecular-weight contaminants, the purified protein is stored frozen or is lyophilized. The purification protocol described is typical for a protein that is expressed in fairly high abundance (i.e., >5% total protein) and accumulates in a soluble state.