Abstract
| Originalsprog | Engelsk |
|---|---|
| Tidsskrift | FEBS Journal |
| Vol/bind | 272 |
| Udgave nummer | 6 |
| Sider (fra-til) | 1440-1453 |
| ISSN | 1742-464X |
| DOI | |
| Status | Udgivet - 2005 |
Bibliografisk note
KEYWORDSextremophiles • phosphoribosyl diphosphate • pyrimidine nucleotide biosynthesis • pyrimidine salvage • thermostable enzymes
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Allosteric regulation of the GTP activated and CTP inhibited uracil phosphoribosyltransferase from the thermophilic archaeon Sulfolobus solfataricus. / Jensen, Kaj Frank; Arent, Susan; Larsen, Sine; Schack, Lise.
I: FEBS Journal, Bind 272, Nr. 6, 2005, s. 1440-1453.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › peer review
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TY - JOUR
T1 - Allosteric regulation of the GTP activated and CTP inhibited uracil phosphoribosyltransferase from the thermophilic archaeon Sulfolobus solfataricus
AU - Jensen, Kaj Frank
AU - Arent, Susan
AU - Larsen, Sine
AU - Schack, Lise
N1 - KEYWORDS extremophiles • phosphoribosyl diphosphate • pyrimidine nucleotide biosynthesis • pyrimidine salvage • thermostable enzymes
PY - 2005
Y1 - 2005
N2 - The upp gene, encoding uracil phosphoribosyltransferase (UPRTase) from the thermoacidophilic archaeon Sulfolobus solfataricus, was cloned and expressed in Escherichia coli. The enzyme was purified to homogeneity. It behaved as a tetramer in solution and showed optimal activity at pH 5.5 when assayed at 60 °C. Enzyme activity was strongly stimulated by GTP and inhibited by CTP. GTP caused an approximately 20-fold increase in the turnover number kcat and raised the Km values for 5-phosphoribosyl-1-diphosphate (PRPP) and uracil by two- and >10-fold, respectively. The inhibition by CTP was complex as it depended on the presence of the reaction product UMP. Neither CTP nor UMP were strong inhibitors of the enzyme, but when present in combination their inhibition was extremely powerful. Ligand binding analyses showed that GTP and PRPP bind cooperatively to the enzyme and that the inhibitors CTP and UMP can be bound simultaneously (KD equal to 2 and 0.5 µm, respectively). The binding of each of the inhibitors was incompatible with binding of PRPP or GTP. The data indicate that UPRTase undergoes a transition from a weakly active or inactive T-state, favored by binding of UMP and CTP, to an active R-state, favored by binding of GTP and PRPP.
AB - The upp gene, encoding uracil phosphoribosyltransferase (UPRTase) from the thermoacidophilic archaeon Sulfolobus solfataricus, was cloned and expressed in Escherichia coli. The enzyme was purified to homogeneity. It behaved as a tetramer in solution and showed optimal activity at pH 5.5 when assayed at 60 °C. Enzyme activity was strongly stimulated by GTP and inhibited by CTP. GTP caused an approximately 20-fold increase in the turnover number kcat and raised the Km values for 5-phosphoribosyl-1-diphosphate (PRPP) and uracil by two- and >10-fold, respectively. The inhibition by CTP was complex as it depended on the presence of the reaction product UMP. Neither CTP nor UMP were strong inhibitors of the enzyme, but when present in combination their inhibition was extremely powerful. Ligand binding analyses showed that GTP and PRPP bind cooperatively to the enzyme and that the inhibitors CTP and UMP can be bound simultaneously (KD equal to 2 and 0.5 µm, respectively). The binding of each of the inhibitors was incompatible with binding of PRPP or GTP. The data indicate that UPRTase undergoes a transition from a weakly active or inactive T-state, favored by binding of UMP and CTP, to an active R-state, favored by binding of GTP and PRPP.
U2 - 10.1111/j.1742-4658.2005.04576.x
DO - 10.1111/j.1742-4658.2005.04576.x
M3 - Journal article
C2 - 15752360
VL - 272
SP - 1440
EP - 1453
JO - F E B S Journal
JF - F E B S Journal
SN - 1742-464X
IS - 6
ER -