In the past funding period three new enzymes and a new intermediate have been discovered in the purine biosynthetic pathway in E. coli. The applicant's laboratory has established that PurK catalyzes the conversion of AIR in an ATP and bicarbonate dependent reaction to the N(5)-carbamate of AIR (N(5)-CAIR). N(5)-CAIR has a half life of 30 sec at 370 C and pH 7.5. PurE then catalyzes an isomerization of this compound to CAIR. The Benkovic and Smith laboratories have discovered a novel, non-folate requiring GAR transformylase. These discoveries, the availability of gram quantities of all of the enzymes in the pathway, and the ability to use these enzymes as reagents to make substrates have set the stage for the goals in the next funding period. The applicant will use a variety of rapid kinetics methods (msec time scale) including rapid stopped-flow UV-vis spectroscopy, rapid chemical quench followed by analysis using HPLC, EPR, Mossbauer, or NMR spectroscopies to examine a number of mechanistic questions. The applicant will investigate: (1) The mechanism of the unusual PurE catalyzed rearrangement reaction; (2) The role of glutamine delivery of """"""""NH3"""""""" to its substrates in PRPP-amidotransferases and FGAR- aminotransferase reactions; (3) The role of the propeptide in B. subtilis and mammalian amidotransferases; and (4) The role of the non- heme iron in and the mechanism of an alpha-ketoglutarate dioxygenase (thymine hydroxylase) involved in pyrimidine metabolism. In addition to the mechanistic work, the applicant will continue to use genetics and kinetic methods to investigate the importance of channeling of chemically unstable intermediates in the purine pathway both in vitro and in vivo. The applicant will continue studies of the channeling of PRA between the first two enzymes in the pathway: PRPP aminotransferase and GAR synthetase. The applicant will also investigate the importance of channeling of the newly discovered N(5)-CAIR between PurE and PurK. She will use enzymes from both prokaryotic and eukaryotic systems to address these questions.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM032191-17
Application #
2734472
Study Section
Biochemistry Study Section (BIO)
Project Start
1987-09-01
Project End
1999-12-31
Budget Start
1998-07-01
Budget End
1999-12-31
Support Year
17
Fiscal Year
1998
Total Cost
Indirect Cost
Name
Massachusetts Institute of Technology
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
City
Cambridge
State
MA
Country
United States
Zip Code
02139
Morar, Mariya; Hoskins, Aaron A; Stubbe, JoAnne et al. (2008) Formylglycinamide ribonucleotide amidotransferase from Thermotoga maritima: structural insights into complex formation. Biochemistry 47:7816-30
Hoskins, Aaron A; Morar, Mariya; Kappock, T Joseph et al. (2007) N5-CAIR mutase: role of a CO2 binding site and substrate movement in catalysis. Biochemistry 46:2842-55
Anand, Ruchi; Hoskins, Aaron A; Stubbe, JoAnne et al. (2004) Domain organization of Salmonella typhimurium formylglycinamide ribonucleotide amidotransferase revealed by X-ray crystallography. Biochemistry 43:10328-42
Anand, Ruchi; Hoskins, Aaron A; Bennett, Eric M et al. (2004) A model for the Bacillus subtilis formylglycinamide ribonucleotide amidotransferase multiprotein complex. Biochemistry 43:10343-52
Hoskins, Aaron A; Anand, Ruchi; Ealick, Steven E et al. (2004) The formylglycinamide ribonucleotide amidotransferase complex from Bacillus subtilis: metabolite-mediated complex formation. Biochemistry 43:10314-27
Zilles, J L; Kappock, T J; Stubbe, J et al. (2001) Altered pathway routing in a class of Salmonella enterica serovar Typhimurium mutants defective in aminoimidazole ribonucleotide synthetase. J Bacteriol 183:2234-40
Kappock, T J; Ealick, S E; Stubbe, J (2000) Modular evolution of the purine biosynthetic pathway. Curr Opin Chem Biol 4:567-72
Mathews, I I; Kappock, T J; Stubbe, J et al. (1999) Crystal structure of Escherichia coli PurE, an unusual mutase in the purine biosynthetic pathway. Structure 7:1395-406
Thoden, J B; Kappock, T J; Stubbe, J et al. (1999) Three-dimensional structure of N5-carboxyaminoimidazole ribonucleotide synthetase: a member of the ATP grasp protein superfamily. Biochemistry 38:15480-92
Li, C; Kappock, T J; Stubbe, J et al. (1999) X-ray crystal structure of aminoimidazole ribonucleotide synthetase (PurM), from the Escherichia coli purine biosynthetic pathway at 2.5 A resolution. Structure 7:1155-66

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