The Crystallization of Proteins with Chiral Precipitants

Abstract

The phase behavior of protein solutions is not yet well understood. The inability to predict protein phase behavior inhibits progress in many biophysical problems such as the crystallization of proteins for structure determination. Our long-term goal is to make it possible to predict the phase behavior of protein solutions. Here we present results on the phase behavior of thaumatin, a globular protein used as a model system in crystallization studies. It is known that the addition of L-tartrate ions leads to the rapid formation of protein crystals, but the available information about the solubility of these crystals is inconsistent. We have determined the solubility of thaumatin with L-, D- and meso-tartrate ions. We find that crystals with the different additives have different solubilities, habits and intermolecular packing. Our results suggest that the chirality of additives may be another useful tool to alter the phase behavior of proteins