Two enzymes are known to catalyse the third step in de novo purine biosynthesis. This enzyme requires ATP and utilizes formate, which is provided by the hydrolysis of 10-formyltetrahydrofolate by EC 3.5.1.10, formyltetrahydrofolate deformylase. The other enzyme, EC 2.1.2.2, phosphoribosylglycinamide formyltransferase 1, utilizes 10-formyltetrahydrofolate directly. Formyl phosphate is formed during catalysis as an intermediate. The enzyme from the bacterium Escherichia coli can also catalyse the activity of EC 2.7.2.1, acetate kinase.
possible catalytic mechanism for PurT transformylase. In this mechanism, the breakage of the beta-gamma phosphate bond results in a shift of the Mg2+-formyl phosphate thereby bringing the carbonyl carbon of the formyl phosphate near the amine of glycinamide ribonucleotide (GAR). Asp268 functions to deprotonate the amine of GAR, which then reacts with the carbonyl group of formyl phosphate to release phosphate and formyl-GAR
Two enzymes are known to catalyse the third step in de novo purine biosynthesis. This enzyme requires ATP and utilizes formate, which is provided by the hydrolysis of 10-formyltetrahydrofolate by EC 3.5.1.10, formyltetrahydrofolate deformylase. The other enzyme, EC 2.1.2.2, phosphoribosylglycinamide formyltransferase 1, utilizes 10-formyltetrahydrofolate directly. Formyl phosphate is formed during catalysis as an intermediate. The enzyme from the bacterium Escherichia coli can also catalyse the activity of EC 2.7.2.1, acetate kinase.
kinetic studies of the wild-type PurT enzyme demonstrate that formyl phosphate behaves as a chemically and kinetically competent intermediate. The requirement for ATP and glycinamide ribonucleotide (GAR) in these reactions is consistent with previous steady-state kinetic results, which have demonstrated that all substrates must be bound before catalysis. Kinetic analysis and positional isotope exchange studies also support the assignment of formyl phosphate as a plausible intermediate. Forward and reverse half-reactions utilizing the proposed intermediate are measured spectrophotometrically. PurT transformylase is capable of generating acetyl phosphate from ATP and acetate. The first half-reaction leads to production of acyl phosphate, the second half-reaction acylates GAR. Neither acetyl GAR nor carbamyl GAR is produced when the enzyme is incubated with ATP, GAR, and the appropriate acid. Neither the reverse first half-reaction with acetyl phosphate nor carbamyl phosphate requires GAR to be present, in contrast to the half-reactions involving formyl phosphate. No activity with aminoformate
radioactive assay monitoring the conversion of [14C]formate to fGAR or [alpha-32P] ATP to ADP. No activity with 10-formyl-5,8-dideazatetrahydrofolate (10-formyl-DDF), 5-formyl-THF, formyl-aminoimidazolecarboxamide ribonucleotide (fAICAR), formylmethionine, and formiminoglutamate as formyl donor. The enzyme shows a side reaction with ATP and acetate: cleavage of ATP in the presence of acetate to generate acetyl phosphate and ADP. The NMR study demonstrates that the purT GAR transformylase reaction proceeds through a transfer of atomic oxygen from formate to the 7-phosphoryl moiety of ATP. One interpretation is the intermediacy of formyl phosphate whose presence is also supported by the identification of acetyl phosphate as a product in the side reaction
key amino acid side chains involved in binding the nonhydrolyzable ATP analogue AMP-PNP to the enzyme include Arg114, Lys155, Glu195, Glu203, and Glu267. Strikingly, the amino group of GAR that is formylated during the reaction lies at 2.8 A from one of the gamma-phosphoryl oxygens of the AMP-PNP
key amino acid side chains involved in binding the nonhydrolyzable ATP analogue AMP-PNP to the enzyme include Arg114, Lys155, Glu195, Glu203, and Glu267. Strikingly, the amino group of GAR that is formylated during the reaction lies at 2.8 A from one of the gamma-phosphoryl oxygens of the AMP-PNP
The purT encoded glycinamide ribonucleotide transformylase differs from the previously known purN encoded enzyme in size, sequence, and substrates, and ATP and formate are required as opposed to formyl tetrahydrofolate
the PurT transformylase belongs to the ATP-grasp superfamily of proteins. The common theme among members of this superfamily is a catalytic reaction mechanism that requires ATP and proceeds through an acyl phosphate intermediate. All of the enzymes belonging to the ATP-grasp superfamily are composed of three structural motifs, termed the A-, B-, and C-domains, and in each case, the ATP is wedged between the B- and C-domains. Superposition of the Rossmann folds found in UDP-galactose 4-epimerase and PurT transformylase, overview
mutants defective in synthesis of purN- and purT-encoded enzymes are isolated. Only strains defective in both genes require an exogenous purine source for growth. Determination of GAR transformylase T activity in vitro requires formate as the Cl donor. Growth of purN mutants is inhibited by glycine. Under these conditions GAR accumulates. Addition of purine compounds or formate prevents growth inhibition
on the basis of the growth of purU, purN, and purU/purN mutants, it appears that PurU provides the major source of formate for the purT-dependent synthesis of 5'-phosphoribosyl-N-formylglycinamide (FGAR). Mutations in either of two pairs of genes are required to block synthesis of FGAR from GAR: purN/purT (purT encodes an alternative formate-dependent GAR transformylase) or purN/purU
PurT transformylase mutant G162I catalyzes the production of formyl GAR two orders of magnitude less efficiently than the wild-type enzyme. This reduced rate is apparently sufficient to sustain cell growth under limiting purine conditions
single mutants of Salmonella enterica serovar Typhimurium strain 4/74, created by deletion of the purN and purT genes, grow as well as the parental wild-type strain in minimal medium, while the double mutant does not grow. Mutation of purN but not purT attenuates the strain during interaction with cultured macrophages. Growth phenotypes of mutants in murine J774A.1 macrophages, overview
single mutants of Salmonella enterica serovar Typhimurium strain 4/74, created by deletion of the purN and purT genes, grow as well as the parental wild-type strain in minimal medium, while the double mutant does not grow. Mutation of purN but not purT attenuates the strain during interaction with cultured macrophages. Growth phenotypes of mutants in murine J774A.1 macrophages, overview
purN- and purT-encoded enzymes are required for synthesis of N2-formyl-N1-(5-phospho-beta-D-ribosyl)glycinamide, both enzymes may function to ensure normal purine biosynthesis. Regulation of the level of GAR transformylase T is controlled by the PurR protein and hypoxanthine. The GAR transformylase T-catalyzed reaction might provide a pathway by which formate is utilized or rescued as a C1 unit, and the activity of the two different GAR transformylases might be determined by the availability of the cofactors, formate and 10-formyl-THF
PurT glycinamide ribonucleotide (GAR) transformylase is an alternative to the formyl-folate utilizing purN GAR transformylase. No significant homology exists between the two transformylases. But the PurT protein shows significant homology to the PurK protein, also involved in purine biosynthesis
formate is required as the one-carbon donor for PurT-dependent synthesis of 5'-phosphoribosyl-N-formylglycinamide (FGAR) and formate is produced in a PurU-dependent reaction
in Escherichia coli, the PurT-encoded glycinamide ribonucleotide transformylase, or PurT transformylase, catalyzes an alternative formylation of glycinamide ribonucleotide (GAR) in the de novo pathway for purine biosynthesis
PurT glycinamide ribonucleotide (GAR) transformylase is an alternative to the formyl-folate utilizing purN GAR transformylase. Biologically relevant transformation of beta-GAR into fGAR
the enzymes PurN and PurT are both essential for systemic infection of mice in Salmonella enterica serovar Typhimurium. PurN and PurT are redundant in vitro but not in vivo
the Escherichia coli purT encoded glycinamide ribonucleotide transformylase (GAR transformylase) serves as an alternate enzyme in the production of formyl GAR for use in de novo purine biosynthesis
the enzymes PurN and PurT are both essential for systemic infection of mice in Salmonella enterica serovar Typhimurium. PurN and PurT are redundant in vitro but not in vivo
specifically in PurT transformylase, the glycinamide ribonucleotide (GAR) substrate is anchored to the protein via Glu82, Asp286, Lys355, Arg362, and Arg363. Structure analysis of the active site for PurT transformylase, overview
specifically in PurT transformylase, the glycinamide ribonucleotide (GAR) substrate is anchored to the protein via Glu82, Asp286, Lys355, Arg362, and Arg363. Structure analysis of the active site for PurT transformylase, overview
the A-domain is formed by segment Thr2-Ala122 and is dominated by a five-stranded parallel beta-pleated sheet flanked on either side by two alpha-helices. The smallest of the three structural motifs of the PurT transformylase, the B-domain is formed by Glu123-Gly196 and contains a four-stranded antiparallel beta-sheet with the strands ranging in length from three to five amino acid residues. The most complicated of the domains, the C-motif extends from Val197 to Gly392 and is composed primarily of an eight-stranded antiparallel beta-pleated sheet formed by Phe202-Ser210, Val215-Gln225, Tyr230-Gln235, Gly262-Val270, Val275-Ser281, Ala321-Ile326, Gln349-Leu352, and Gly365-Thr370. There are two additional regions of antiparallel beta-sheet formed by Gln329-Ser332 and Ile358-Ser361 and Thr336-Asp338 and Val388-Gly392, respectively. The four alpha-helices located in the C-domain range in length from four to eighteen amino acid residues. There are seven classical reverse turns in the C-domain that link these various beta-strands and alpha-helices together (three type I, one type I', one type II, one type II', and one type III). The dimeric interface is formed from regions provided by both the A- and C-domains. Enzyme structure analysis, detailed overview
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CRYSTALLIZATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
purified enzyme complexed with the nonhydrolyzable ATP analogue AMP-PNP and complexed with AMP-PNP and glycinamide ribonucleotide, hanging drop vapor diffusion method, mixing of 20 mg/ml protein in 15 mM HEPES, pH 7.5, 5 mM AMP-PNP, 10 mM MgCl2, and 250 mM NaCl, in an 1:1 ratio with reservoir solution containing 18-22% w/v methyl ether poly(ethylene glycol) 5000, 100 mM MOPS, pH 6.7, and 100 mM MgCl2, 4°C, 2-3 weeks, X-ray diffraction structure determination analysis at 1.9 A resolution. For preparation of the complex with GAR, crystals grown in the presence of AMP-PNP are transferred to a solution containing 20% w/v methyl ether poly(ethylene glycol) 5000, 50 mM MgCl2, 350 mM NaCl, 2.5 mM AMP-PNP, 100 mM MOPS (pH 6.7), and 1 mM GAR, the crystals are allowed to soak for 12 h, X-ray diffraction structure determination analysis at 1.75 A resolution. Structure modelling, detailed overview
isolation of mutants defective in GAR transformylase activity, generation of single and double null mutants of genes purT and purN, phenotypes, overview
isolation of mutants defective in GAR transformylase activity, generation of single and double null mutants of genes purT and purN, phenotypes, overview
single mutants of Salmonella enterica serovar Typhimurium strain 4/74 are created by deletion of the purN and purT genes, generation of different purT (encoding formyltetrahydrofolate deformylase, EC 3.5.1.10) and purU mutants. The DELTApurU/DELTApurT mutant shows increased virulence in macophages compared to wild-type, while all other mutants have reduced virulence. purN and purT mutants grow somewhat slower than the wild-type. Mutation of purN but not purT attenuates the strain during interaction with cultured macrophages. Single-gene deletions of each of the purT and purN causes in mouse infections. While the DELTApurT mutant multiplies as fast as the wild-type strain in cultured J774A.1 macrophages, net multiplication of the DELTApurN mutant is reduced approximately 50% in 20 h. The attenuation of the DELTApurT mutant is abolished by simultaneous removal of the enzyme PurU, responsible for the formation of formate, indicating that the attenuation is related to formate accumulation or wasteful consumption of formyl tetrahydrofolate by PurU
single mutants of Salmonella enterica serovar Typhimurium strain 4/74 are created by deletion of the purN and purT genes, generation of different purT (encoding formyltetrahydrofolate deformylase, EC 3.5.1.10) and purU mutants. The DELTApurU/DELTApurT mutant shows increased virulence in macophages compared to wild-type, while all other mutants have reduced virulence. purN and purT mutants grow somewhat slower than the wild-type. Mutation of purN but not purT attenuates the strain during interaction with cultured macrophages. Single-gene deletions of each of the purT and purN causes in mouse infections. While the DELTApurT mutant multiplies as fast as the wild-type strain in cultured J774A.1 macrophages, net multiplication of the DELTApurN mutant is reduced approximately 50% in 20 h. The attenuation of the DELTApurT mutant is abolished by simultaneous removal of the enzyme PurU, responsible for the formation of formate, indicating that the attenuation is related to formate accumulation or wasteful consumption of formyl tetrahydrofolate by PurU
recombinant enzyme from Escherichia coli strain BL21(DE3) by streptomycin sulfate precipitation, anion exchange chromatography, ultrafiltration, dialysis, and gel filtration, followed by dialysis and ultrafiltration
recombinant enzyme from Escherichia coli strain TX635 by streptomycin sulfate precipitation, dialysis, anion exchange chromatography, and ultrafiltration, followed by another different step of anion exchange chromatography, dialysis, and ultrafiltration
recombinant wild-type and mutant enzymes from TX680 auxotrophic cells by gel filtration, anion exchange chromatography, and dialysis, to over 90% purity
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EXPRESSION
ORGANISM
UNIPROT
LITERATURE
regulation of the level of GAR transformylase T is controlled by the PurR protein and hypoxanthine. The purT operator sequence for PurR binding is similar to that reported for several pur regulons, and the gene is a single gene operon
Nagy, P.; Marolewski, A.; Benkovic, S.; Zalkin, H.
Formyltetrahydrofolate hydrolase, a regulatory enzyme that functions to balance pools of tetrahydrofolate and one-carbon tetrahydrofolate adducts in Escherichia coli