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Effects of Protein Purity and Precipitant Stereochemistry on the Crystallization of Thaumatin

Summary: Articles
Effects of Protein Purity and Precipitant Stereochemistry on the
Crystallization of Thaumatin
Neer Asherie,* Charles Ginsberg, Arieh Greenbaum, Samuel Blass, and Sarah Knafo
Department of Physics and Department of Biology, YeshiVa UniVersity,
New York, New York 10033-3312
ReceiVed June 12, 2008; ReVised Manuscript ReceiVed August 21, 2008
ABSTRACT: Thaumatin is frequently used as a model protein in crystallization studies because it rapidly forms crystals in the
presence of tartrate ions. The thermodynamic and kinetic properties of thaumatin crystals have been studied for almost 10 years, and
the results are contradictory. Here we show that by using a homogeneous preparation of thaumatin and controlling the stereochemistry
of the tartrate precipitant, it is possible to achieve consistent results for the protein solubility. To understand the role of protein
impurities in the crystallization of thaumatin, we examined two commercial sources of the protein and characterized the heterogeneities
therein. To examine the effect of precipitant stereochemistry, we crystallized thaumatin with L, D, and DL (racemic) tartrate ions. We
suggest that the inconsistencies among previous results stem in part from the different behavior of thaumatin with the L and D
enantiomers: the solubility of thaumatin crystals increases with temperature in L-tartrate, whereas it decreases with temperature in
D-tartrate. Our results demonstrate the importance of using pure protein and stereochemically pure precipitants in the crystallization
of proteins.
1. Introduction
It has been more than 160 years since the first protein crystals
were reported,1


Source: Asherie, Neer - Departments of Physics & Biology, Yeshiva University


Collections: Biology and Medicine; Physics