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Xavier Lee, Ph.D.
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Area of general research interest:
Protein structure and interaction between proteins and nucleic acid. Current program:
Investigators:
Collaborators:
Brief Description: Structure determination of MPA lectin. Maclura pomifera agglutinin (MPA), from a plant of the Moraceae family, has been shown to be specific for the T-antigen Galb1,3GalNAca, a core structure of the O-linked type of glycopeptide. The binding-site appears to have two subsites. Its sequence, specificity for carbohydrate and its lack of metal ions and disulfide bonds all indicate MPA to be a member of a new lectin family. Protein crystallography has been used to determine the structure of the native form of MPA and its complex with T-antigen. The results will extend our knowledge of biological recognition of this major type of glycopepetide. It would also give a structural basis to the extensive information on the physical properties of the Moraceae lectins, in particular the thermodynamics and kinetics of carbohydrate binding. Two data sets have been collected for the MAD. The structure determination is underway. Structure determination of glutamyl -tRNA-synthetase is a project with important implication for understanding the protein-nucleic acid interaction and recognition. Small crystals of the complex have been obtained. Efforts arebeing made to get usable crystals for structure determination. Crystallization of the TU-elongation factor and catalase from halophilic bacteria. The proteins of halophilic bacteria, such as the TU-elongation factor and the catalase, provide us a model of proteins functioning under extreme environmental conditions (4M NaC1). Attempts to crystallize these proteins have long been made in Europe and in the United States but without success. A collaboration has been established between the laboratory of Dr. J. Zaccai and the x-ray structural analysis laboratory in CCF to start the crystallization of these two proteins. Studies of PKR in solution with Neutron small angle scattering. The antiviral activity of the interferon-induced, double-stranded RNA (dsRNA) activated protein kinase (PKR) is mediated through dsRNA binding leading to PKR autophosphorylation and subsequent inhibition of protein synthesis. Neutron small angle scattering shows that PKR exists in solution predominantly as a dimer. Addition of TAR RNA to PKR causes a significant conformational shift in the protein at a 2:1 stoichiometric ratio of protein to RNA. Titration of PKR with TAR RNA results in a cooperative increase in the size of the molecular complex. Taken together, these data indicate that the PKR activation complex consists of a protein dimer bound cooperatively to one dsRNA molecule. Key References: Zhu DW, Dahms T, Willis K, Szabo AG, Lee X. Crystallization and the preliminary crystallographic studies of the Azurin from Pseudomonas fluorescens. Archives of Biochemistry and Biophysics 308: 469-470, 1994. Dong BH, Xu L, Zhou A, Hassel BA, Lee X, Torrence PF, Silverman RH. Intrinsic molecular activities of the interferon-induced 2-5A-dependent RNase. J. Biol. Chem. 269:14153-14158, 1994. Gomis-Ruth FX, Kress LF, Kellermann J, Mayr I, Lee X, Huber R, Bode W. Refined 2-0 angstrom X-ray crystal structure of the snake venom zinc-endopeptidase Adamalysin II. J. Mol. Biol. 239:513-544, 1994. Zhu DW, Lee X, Labrie F, and Lin S-X. Crystal growth of human estrogenic 17b-hydroxysteroid dehydrogenase. Acta Cryst. D50, 550-551, 1994. Jia Z, Hasnain S, Hirama T, Lee X, Mort JS, To R, Huber CP. Crystal structures of recombinant rat cathepsin B and a Cathepsin B-inhibitor complex: Implecations for Structure-based Inhibitor Design. J. Biol. Chem. 270: 5627-5533, 1995. | ||