Crystallization of the E. coli polyamine-induced protein: a novel procedure based on the concept of ionic strength reducers

Nucleation and growth of macromolecular crystals occur in supersaturated so lutions the properties of which depend on numerous parameters that influenc e macromolecular solubility. Detailed knowledge of the effects of those par ameters is essential for crystallization. The concept of the so-called "ion ic strength reducers" provides insight into the changes of solubility induc ed by organic solvents and hydrophilic polymers in aqueous electrolytic sol utions. A simple and efficient procedure is presented which exploits the pr operties of ionic strength reducers in the crystallization of proteins. Usi ng this procedure in the crystallization of the E. coli polyamine-induced p rotein, superior crystals compared to conventional techniques have been obt ained. The procedure combines microseeding with dialysis techniques and is applicable to other proteins, particularly in cases where conditions favori ng both for nucleation and growth cannot be found, or in cases where excess ive nucleation leads to the growth of a large number of very small crystals . (C) 2000 Elsevier Science B.V. All rights reserved.