The broad long term objectives of this proposal are directed at understanding the relationship between structure and function in biological systems. This application is targeted at carbamoyl phosphate synthetase (CPS); an enzyme that is responsible for the production of the key intermediate during the biosynthesis of arginine (via the urea cycle) and the pyrimidine nucleotides in all types of cells.
The specific aims of this proposal include the following: (1) The chemical reaction catalyzed by this enzyme is quite complex since five substrates are converted to five separate products. The free energy profiles, and spectroscopic identification of reaction intermediates (carboxyphosphate, carbamate, carbon dioxide, and gamma-glutamyl thioester) will be determined by a coordinated program of steady state, rapid quench, and NMR experimental protocols. (2) The bacterial enzyme is composed of two subunits of unequal size. The elucidation of the functional domain boundaries and the role of individual amino acids in binding, catalysis, and regulatory control of this enzyme will be determined by the design, construction, and functional characterization of site-directed and randam mutants. (3) The large synthetase subunit contains a large internal tandem repeat of approximately 400 residues. The functional and structural differences between these two homologous domains will be determined by the creation and characterization of chimeric tandem repeats of either the N-terminal or C-terminal portion of the wild type enzyme. (4) The coordinated control of the reaction intermediates within this enzyme serves as a well-behaved model system for the channeling of reaction products between successive enzymes within a metabolic pathway. The relationship between the binding sites for the production of carbamoyl phosphate will be determined by the elucidation of the three dimensional structure of the enzyme by x-ray diffraction methods on single protein crystals.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK030343-19
Application #
6176487
Study Section
Physical Biochemistry Study Section (PB)
Program Officer
Sechi, Salvatore
Project Start
1982-01-01
Project End
2001-08-31
Budget Start
2000-09-01
Budget End
2001-08-31
Support Year
19
Fiscal Year
2000
Total Cost
$196,781
Indirect Cost
Name
Texas A&M University
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
047006379
City
College Station
State
TX
Country
United States
Zip Code
77845
Meyer, Megan E; Gutierrez, Jemy A; Raushel, Frank M et al. (2010) A conserved glutamate controls the commitment to acyl-adenylate formation in asparagine synthetase. Biochemistry 49:9391-401
Lund, Liliya; Fan, Yubo; Shao, Qiang et al. (2010) Carbamate transport in carbamoyl phosphate synthetase: a theoretical and experimental investigation. J Am Chem Soc 132:3870-8
Fan, Yubo; Lund, Liliya; Shao, Qiang et al. (2009) A combined theoretical and experimental study of the ammonia tunnel in carbamoyl phosphate synthetase. J Am Chem Soc 131:10211-9
Williams, Lakenya; Fresquet, Vicente; Santander, Patricio J et al. (2007) The multiple amidation reactions catalyzed by Cobyric acid synthetase from Salmonella typhimurium are sequential and dissociative. J Am Chem Soc 129:294-5
Thoden, James B; Huang, Xinyi; Kim, Jungwook et al. (2004) Long-range allosteric transitions in carbamoyl phosphate synthetase. Protein Sci 13:2398-405
Fresquet, Vicente; Thoden, James B; Holden, Hazel M et al. (2004) Kinetic mechanism of asparagine synthetase from Vibrio cholerae. Bioorg Chem 32:63-75
Kim, Jungwook; Raushel, Frank M (2004) Access to the carbamate tunnel of carbamoyl phosphate synthetase. Arch Biochem Biophys 425:33-41
Kim, Jungwook; Raushel, Frank M (2004) Perforation of the tunnel wall in carbamoyl phosphate synthetase derails the passage of ammonia between sequential active sites. Biochemistry 43:5334-40
Fresquet, Vicente; Williams, LaKenya; Raushel, Frank M (2004) Mechanism of cobyrinic acid a,c-diamide synthetase from Salmonella typhimurium LT2. Biochemistry 43:10619-27
Raushel, Frank M; Thoden, James B; Holden, Hazel M (2003) Enzymes with molecular tunnels. Acc Chem Res 36:539-48

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