Lorena Sue Beese
James B. Duke Professor of Medicine
The broad goal of our research is to understand biological processes in atomic detail. A multi-disciplinary strategy is employed using macromolecular X-ray crystallography to determine high resolution, three-dimensional images of proteins and appropriate complexes. The structural information is combined with biochemical, genetic, and computational analyses to address questions central to cancer biology. In addition, this approach may facilitate the development new therapeutic agents for the treatment cancer and other diseases.
Numerous signal transduction proteins, including members of the Ras GTPase superfamily, require posttranslational attachment of an isoprenoid lipid group for proper function. A major focus of the lab is on understanding the structural enzymology of the protein prenyltransferase family of lipid modifying enzymes. We have determined high resolution, three-dimensional structures of human protein farnesyltransferase (FTase), an enzyme that is considered a promising anticancer drug target. Inhibitors of FTase cause tumor regression in animals and are currently being evaluated in clinical trials for the treatment of human cancer. Subsequently, we have determined a complete series of structures representing the major steps along the reaction coordinate of this enzyme. From these observations can be deduced the structural determinants of substrate specificity and an unusual mechanism in which product release requires binding of substrate, analogous to classically processive enzymes.
Structure based drug design.
More than 300 patent applications have been made so far for prenyltransferase inhibitors, and at least six are currently in clinical trials. The laboratory is using structural differences among protein prenyltransferases to develop highly specific inhibitors. Our laboratory has determined the mechanism of action of peptidomemetic inhibitors that showed tumor regression in animal studies and are currently investigating chemotherapreutics used in clinical trials for treatment of human cancer. The structures facilitate the design new drugs targeting the prenyltransferase enzyme family. Inhibitors that specifically target the prenyltransferase of pathogens such as Plasmodium falciparum or Trypanosoma brucei may lead to improved treatments for diseases like maleria.
DNA Mismatch Repair.
The laboratory is investigating protein DNA assemblies involved in human mismatch repair. Mismatch repair is essential for maintaining genomic stability of all organisms. Defects in genes involved in mismatch repair lead to elevated mutation rates, and in the case of humans confer a strong predisposition to tumorigenesis. Currently, experiments are focused on determining structures of protein-DNA assemblies involved in the initiation of the human mismatch repair reaction.
A major focus is on understanding the molecular mechanisms of DNA replication. We have determined high-resolution crystal structures of DNA polymerases with DNA primer-templates that capture different stages of the synthesis reaction. Of particular interest is the Bacillus DNA polymerase that retains its ability for processive, accurate DNA synthesis in the crystal. We are using this polymerase as a model system to study molecular mechanisms of DNA mispair incorporation and action of carcinogens that can lead to mutations.
Observing Enzymes in Action.
A common theme of the laboratory is the study of enzyme mechanisms at near atomic resolution by determining three-dimensional structures that represent stages along the reaction pathway. Structural information is combined with biochemical, biophysical, and computational analyses to understand how enzymes function. An exciting new direction arises from the observation that one of the DNA polymerases retains catalytic activity in the crystal (see above). Currently, we are developing methodology to study the phosphoryl-transfer reaction using time-resolved crystallography. Our goal is to observe DNA synthesis in real time. Ultimately, this many enable the dynamic process of accurate DNA replication to be viewed and constrasted with replication under mutagenic conditions.
Current Appointments & Affiliations
Education, Training, & Certifications
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