DMA replication, recombination, and repair are processes fundamental for the transmission of genetic information from one generation of cells to the next. These processes require that duplex DMA is transiently unwound to form a single-stranded intermediate. The unwinding reaction is catalyzed by a class of enzymes called helicases. Helicases are essential for all aspects of nucleic acid metabolism in which ss nucleic acid intermediates are required. Therefore, it is of fundamental importance to understand the molecular mechanism by which these enzymes function in performing their activities. Knowledge of the mechanistic details of the reactions catalyzed by helicases is essential for our understanding of why such processes dysfunction in various diseases; e.g.; cancer and human genetic diseases. Studying different steps on the molecular level will provide the necessary knowledge about how to regulate and control them. This knowledge, in turn, will be very useful in designing efficient therapies for diseases. As a primary replicative helicase in E. Coli cells, the DnaB protein provides an outstanding and paradigm model system to study the molecular mechanism of the replicative helicase. The replicative helicase does not act alone. In the cell, the DnaB helicase is linked to the replication apparatus through the specific replication factor, the DnaC protein. .The DnaB - DnaC complex constitutes a fundamental model of the role of a specific replication factor that connects the helicase to the rest of the replication machine and controls the activities of the enzyme. This research project has three major objectives: The first major objective is to examine the dynamics and energetics of the conformational heterogeneity of the DnaB hexamer and its complex with the DnaC protein. This objective can be achieved by quantitatively examining the thermodynamics and kinetics of conformational transitions and assembly reactions of the DnaB and DnaB-DnaC complex. The second objective is to determine the DnaB - DnaC complex interactions with the ssDNA and the replication fork and the mechanism of the dsDNA unwinding. This objective can be achieved by obtaining detailed kinetics of the individual steps involved in the DNA recognition and unwinding reactions. The third major objective is to determine the dynamics of the formation of DnaB - DnaC complexes and the role of ATP, ADP, and the DNA in this process. To achieve these goals, we will apply steady-state, lifetime fluorescence spectroscopy, the fluorescence energy transfer method, fast kinetic (stopped-flow, rapid quench-flow) methods, dynamic light scattering and analytical ultracentrifugation.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM046679-14
Application #
7060311
Study Section
Molecular and Cellular Biophysics Study Section (BBCA)
Program Officer
Lewis, Catherine D
Project Start
1992-09-30
Project End
2009-04-30
Budget Start
2006-05-01
Budget End
2007-04-30
Support Year
14
Fiscal Year
2006
Total Cost
$280,158
Indirect Cost
Name
University of Texas Medical Br Galveston
Department
Biochemistry
Type
Schools of Medicine
DUNS #
800771149
City
Galveston
State
TX
Country
United States
Zip Code
77555
Bujalowski, Wlodzimierz; Jezewska, Maria J (2014) Quantitative Thermodynamic Analyses of Spectroscopic Titration Curves. J Mol Struct 1077:40-50
Szymanski, Michal R; Jezewska, Maria J; Bujalowski, Wlodzimierz (2013) Energetics of the Escherichia coli DnaT protein trimerization reaction. Biochemistry 52:1858-73
Szymanski, Michal R; Jezewska, Maria J; Bujalowski, Wlodzimierz (2013) The Escherichia coli primosomal DnaT protein exists in solution as a monomer-trimer equilibrium system. Biochemistry 52:1845-57
Bujalowski, Wlodek M; Jezewska, Maria J (2012) Fluorescence intensity, anisotropy, and transient dynamic quenching stopped-flow kinetics. Methods Mol Biol 875:105-33
Bujalowski, Wlodek M; Jezewska, Maria J (2012) Using structure-function constraints in FRET studies of large macromolecular complexes. Methods Mol Biol 875:135-64
Szymanski, Michal R; Jezewska, Maria J; Bujalowski, Wlodzimierz (2011) Binding of two PriA-PriB complexes to the primosome assembly site initiates primosome formation. J Mol Biol 411:123-42
Szymanski, Michal R; Bujalowski, Paul J; Jezewska, Maria J et al. (2011) The N-terminal domain of the Escherichia coli PriA helicase contains both the DNA- and nucleotide-binding sites. Energetics of domain--DNA interactions and allosteric effect of the nucleotide cofactors. Biochemistry 50:9167-83
Bujalowski, Wlodzimierz; Jezewska, Maria J (2011) Macromolecular competition titration method accessing thermodynamics of the unmodified macromolecule-ligand interactions through spectroscopic titrations of fluorescent analogs. Methods Enzymol 488:17-57
Szymanski, Michal R; Jezewska, Maria J; Bujalowski, Wlodzimierz (2010) The Escherichia coli PriA helicase-double-stranded DNA complex: location of the strong DNA-binding subsite on the helicase domain of the protein and the affinity control by the two nucleotide-binding sites of the enzyme. J Mol Biol 402:344-62
Updegrove, Taylor B; Correia, John J; Galletto, Roberto et al. (2010) E. coli DNA associated with isolated Hfq interacts with Hfq's distal surface and C-terminal domain. Biochim Biophys Acta 1799:588-96

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