W0248

The Influence of Turkey Egg-White Lysozyme on Chicken Egg-White Lysozyme Crystallization. Constance Schall, Venkat Bhamidi, B. Leif Hanson and Allen Edmundson Chemical & Environmental Engineering, University of Toledo, Toledo, OH 43606 USA

Crystallization is the paramount first step in the determination of large protein structures and an important isolation mechanism for pure product. Structure determination of proteins is crucial to an understanding of structure function relationships, the rational development of strategies for disease treatment and pharmaceutical development, and the development and generation of new applications in enzymatic catalysis. Even highly purified protein solutions will contain impurities that can inhibit growth and increase disorder of protein crystals and limit terminal crystal size. Crystal growth in the presence of impurities is the rule rather than the exception. The critical question then becomes; how can crystal growth be optimized in the presence of impurities?

Nucleation and growth of chicken egg-white lysozyme (HEWL) crystals in the presence of a protein impurity, turkey egg white lysozyme (TEWL) was examined. Incorporation TEWL was measured using high performance liquid chromagraphy.

In preliminary batch experiments TEWL additions did not significantly effect nucleation of HEWL crystallization. Additions of TEWL resulted in a change of HEWL habit. Growth of [110] faces of lysozyme appeared to be inhibited with TEWL. With increasing supersaturation, the effects of TEWL on inhibition of growth of the [110] face of HEWL were diminished. The results suggest that the underlying principles are consistent with those observed in small molecule crystallization. The partitioning of TEWL into HEWL crystals appears to be dependent upon the concentration of TEWL and HEWL in solution.

Inhibition of growth of HEWL crystals by TEWL is hypothesized to be due to a change in amino acid composition at residue 41 from a glutamine in HEWL to histidine in TEWL.