The role of enzyme isomerization in the native catalytic cycle of the ATP sulfurylase-GTPase system

Jiang Wei, Changxian Liu, Thomas S. Leyh

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

ATP sulfurylase, from E. coli K-12, is a GTPase·target complex that conformationally couples the free energies of GTP hydrolysis and activated sulfate (adenosine 5'-phosphosulfate, or APS) synthesis. Energy coupling is achieved by an allosterically driven isomerization that switches on and off chemistry at specific points in the catalytic cycle. This coupling mechanism is derived from the results of model studies using analogue complexes that mimic different stages of the native catalytic cycle. The current investigation extends the analogue studies to the native catalytic cycle. Isomerization is monitored using the fluorescent, guanine nucleotide analogues mGMPPNP (3'-O-(N-methylanthraniloyl)-2'-deoxyguanosine 5'-[β,γ- imido]triphosphate) and mGTP [3'-O-(N-methylanthraniloyl)-2'-deoxyguanosine 5'-triphosphate]. The isomerization is shown to be initiated by an allosteric interaction that requires the simultaneous occupancy of all three substrate- binding sites. Stopped-flow fluorescence and single-turnover studies were used to define and quantitate the isomerization mechanism, and to show that the isomerization precedes and rate-limits both GTP hydrolysis and APS synthesis. These findings are incorporated into a model of the energy- coupling mechanism.

Original languageEnglish (US)
Pages (from-to)4704-4710
Number of pages7
JournalBiochemistry
Volume39
Issue number16
DOIs
StatePublished - Apr 25 2000

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Sulfate Adenylyltransferase
GTP Phosphohydrolases
Isomerization
Guanosine Triphosphate
Adenosine Phosphosulfate
Hydrolysis
Guanine Nucleotides
Enzymes
Sulfates
Fluorescence
Binding Sites
Escherichia coli
Free energy
Switches
Substrates

ASJC Scopus subject areas

  • Biochemistry

Cite this

The role of enzyme isomerization in the native catalytic cycle of the ATP sulfurylase-GTPase system. / Wei, Jiang; Liu, Changxian; Leyh, Thomas S.

In: Biochemistry, Vol. 39, No. 16, 25.04.2000, p. 4704-4710.

Research output: Contribution to journalArticle

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