UniProt functional annotation for P0A7E5



	UniProt functional annotation for P0A7E5

UniProt code: P0A7E5.

Organism: Escherichia coli (strain K12).

Taxonomy: Bacteria; Proteobacteria; Gammaproteobacteria; Enterobacterales; Enterobacteriaceae; Escherichia.

Function: Catalyzes the ATP-dependent amination of UTP to CTP with either L-glutamine or ammonia as the source of nitrogen. Regulates intracellular CTP levels through interactions with the four ribonucleotide triphosphates. {ECO:0000269|PubMed:11336655, ECO:0000269|PubMed:8385490, ECO:0000305|PubMed:15157079}.

Catalytic activity: Reaction=ATP + H2O + L-glutamine + UTP = ADP + CTP + 2 H(+) + L- glutamate + phosphate; Xref=Rhea:RHEA:26426, ChEBI:CHEBI:15377, ChEBI:CHEBI:15378, ChEBI:CHEBI:29985, ChEBI:CHEBI:30616, ChEBI:CHEBI:37563, ChEBI:CHEBI:43474, ChEBI:CHEBI:46398, ChEBI:CHEBI:58359, ChEBI:CHEBI:456216; EC=6.3.4.2; Evidence={ECO:0000269|PubMed:11336655, ECO:0000269|PubMed:4550559, ECO:0000269|PubMed:8385490};

Activity regulation: Allosterically activated by GTP, when glutamine is the substrate; GTP has no effect on the reaction when ammonia is the substrate (PubMed:4550559). The allosteric effector GTP functions by stabilizing the protein conformation that binds the tetrahedral intermediate(s) formed during glutamine hydrolysis (PubMed:11336655). Also activated by magnesium; the enzyme requires more Mg(2+) for full catalytic activity than required simply to complex the nucleotide substrates (PubMed:8385490). Inhibited by the product CTP, via allosteric rather than competitive inhibition (PubMed:8385490, PubMed:16216072). Also inhibited by divalent metal ions such as copper and zinc (PubMed:8385490). Is potently inhibited by the intermediate analog inhibitor glutamate gamma-semialdehyde (PubMed:11336655). {ECO:0000269|PubMed:11336655, ECO:0000269|PubMed:4550559, ECO:0000269|PubMed:8385490, ECO:0000305|PubMed:16216072}.

Biophysicochemical properties: Kinetic parameters: KM=2.0 mM for ammonia {ECO:0000269|PubMed:11336655}; KM=0.30 mM for L-glutamine (in the presence of 0.25 mM GTP) {ECO:0000269|PubMed:11336655}; Note=kcat is 13 sec(-1) with ammonia as substrate. kcat is 6.6 sec(- 1) with L-glutamine as substrate (in the presence of 0.25 mM GTP). {ECO:0000269|PubMed:11336655}; pH dependence: Optimum pH is 8.7. {ECO:0000269|PubMed:8385490};

Pathway: Pyrimidine metabolism; CTP biosynthesis via de novo pathway; CTP from UDP: step 2/2. {ECO:0000255|HAMAP-Rule:MF_01227}.

Subunit: Homodimer that associates to form homotetramer in the presence of ATP and UTP. The substrate nucleotides ATP and UTP act synergistically to promote oligomerization of CTPS from inactive dimers to active tetramers. {ECO:0000269|PubMed:4550560}.

Subcellular location: Cytoplasm {ECO:0000269|PubMed:32507415}. Note=Localizes to the cytoophidium, a subcellular filamentary structure where CTP synthase is compartmentalized. Many cells form cytoophidia which are observed in stationary phase. {ECO:0000269|PubMed:32507415}.

Domain: Sequence consists of two domains: the C-terminal glutamine amide transfer (GAT) domain catalyzes the hydrolysis of glutamine; the N-terminal synthase domain catalyzes the amination of UTP (PubMed:3514618, PubMed:3298209). Structure shows each subunit consists of three distinct segments: the N-terminal amidoligase (ALase) domain, which mediates oligomerization and contains the ALase active site where ATP and UTP substrates bind, and an interrupted helical interdomain linker segment that connects the ALase domain to the Type I glutamine amidotransferase (GATase) C-terminal domain, which generates ammonia via glutamine hydrolysis (PubMed:15157079). A gated channel that spans 25 Angstroms between the glutamine hydrolysis and amidoligase active sites provides a path for ammonia diffusion; the channel is accessible to solvent at the base of a cleft adjoining the glutamine hydrolysis active site, providing an entry point for exogenous ammonia (PubMed:15157079). {ECO:0000305|PubMed:15157079, ECO:0000305|PubMed:3298209, ECO:0000305|PubMed:3514618}.

Miscellaneous: CTPSs have evolved a hybrid strategy for distinguishing between UTP and CTP. The overlapping regions of the product feedback inhibitory and substrate sites recognize a common feature in both compounds, the triphosphate moiety. To differentiate isosteric substrate and product pyrimidine rings, an additional pocket far from the expected kinase/ligase catalytic site, specifically recognizes the cytosine and ribose portions of the product inhibitor. {ECO:0000305|PubMed:16216072}.

Similarity: Belongs to the CTP synthase family. {ECO:0000255|HAMAP- Rule:MF_01227}.

Annotations taken from UniProtKB at the EBI.


Organism:		Escherichia coli (strain K12).
Taxonomy:		Bacteria; Proteobacteria; Gammaproteobacteria; Enterobacterales; Enterobacteriaceae; Escherichia.



Function:		Catalyzes the ATP-dependent amination of UTP to CTP with either L-glutamine or ammonia as the source of nitrogen. Regulates intracellular CTP levels through interactions with the four ribonucleotide triphosphates. {ECO:0000269\|PubMed:11336655, ECO:0000269\|PubMed:8385490, ECO:0000305\|PubMed:15157079}.


Catalytic activity:		Reaction=ATP + H2O + L-glutamine + UTP = ADP + CTP + 2 H(+) + L- glutamate + phosphate; Xref=Rhea:RHEA:26426, ChEBI:CHEBI:15377, ChEBI:CHEBI:15378, ChEBI:CHEBI:29985, ChEBI:CHEBI:30616, ChEBI:CHEBI:37563, ChEBI:CHEBI:43474, ChEBI:CHEBI:46398, ChEBI:CHEBI:58359, ChEBI:CHEBI:456216; EC=6.3.4.2; Evidence={ECO:0000269\|PubMed:11336655, ECO:0000269\|PubMed:4550559, ECO:0000269\|PubMed:8385490};
Activity regulation:		Allosterically activated by GTP, when glutamine is the substrate; GTP has no effect on the reaction when ammonia is the substrate (PubMed:4550559). The allosteric effector GTP functions by stabilizing the protein conformation that binds the tetrahedral intermediate(s) formed during glutamine hydrolysis (PubMed:11336655). Also activated by magnesium; the enzyme requires more Mg(2+) for full catalytic activity than required simply to complex the nucleotide substrates (PubMed:8385490). Inhibited by the product CTP, via allosteric rather than competitive inhibition (PubMed:8385490, PubMed:16216072). Also inhibited by divalent metal ions such as copper and zinc (PubMed:8385490). Is potently inhibited by the intermediate analog inhibitor glutamate gamma-semialdehyde (PubMed:11336655). {ECO:0000269\|PubMed:11336655, ECO:0000269\|PubMed:4550559, ECO:0000269\|PubMed:8385490, ECO:0000305\|PubMed:16216072}.
Biophysicochemical properties:		Kinetic parameters: KM=2.0 mM for ammonia {ECO:0000269\|PubMed:11336655}; KM=0.30 mM for L-glutamine (in the presence of 0.25 mM GTP) {ECO:0000269\|PubMed:11336655}; Note=kcat is 13 sec(-1) with ammonia as substrate. kcat is 6.6 sec(- 1) with L-glutamine as substrate (in the presence of 0.25 mM GTP). {ECO:0000269\|PubMed:11336655}; pH dependence: Optimum pH is 8.7. {ECO:0000269\|PubMed:8385490};
Pathway:		Pyrimidine metabolism; CTP biosynthesis via de novo pathway; CTP from UDP: step 2/2. {ECO:0000255\|HAMAP-Rule:MF_01227}.
Subunit:		Homodimer that associates to form homotetramer in the presence of ATP and UTP. The substrate nucleotides ATP and UTP act synergistically to promote oligomerization of CTPS from inactive dimers to active tetramers. {ECO:0000269\|PubMed:4550560}.
Subcellular location:		Cytoplasm {ECO:0000269\|PubMed:32507415}. Note=Localizes to the cytoophidium, a subcellular filamentary structure where CTP synthase is compartmentalized. Many cells form cytoophidia which are observed in stationary phase. {ECO:0000269\|PubMed:32507415}.
Domain:		Sequence consists of two domains: the C-terminal glutamine amide transfer (GAT) domain catalyzes the hydrolysis of glutamine; the N-terminal synthase domain catalyzes the amination of UTP (PubMed:3514618, PubMed:3298209). Structure shows each subunit consists of three distinct segments: the N-terminal amidoligase (ALase) domain, which mediates oligomerization and contains the ALase active site where ATP and UTP substrates bind, and an interrupted helical interdomain linker segment that connects the ALase domain to the Type I glutamine amidotransferase (GATase) C-terminal domain, which generates ammonia via glutamine hydrolysis (PubMed:15157079). A gated channel that spans 25 Angstroms between the glutamine hydrolysis and amidoligase active sites provides a path for ammonia diffusion; the channel is accessible to solvent at the base of a cleft adjoining the glutamine hydrolysis active site, providing an entry point for exogenous ammonia (PubMed:15157079). {ECO:0000305\|PubMed:15157079, ECO:0000305\|PubMed:3298209, ECO:0000305\|PubMed:3514618}.
Miscellaneous:		CTPSs have evolved a hybrid strategy for distinguishing between UTP and CTP. The overlapping regions of the product feedback inhibitory and substrate sites recognize a common feature in both compounds, the triphosphate moiety. To differentiate isosteric substrate and product pyrimidine rings, an additional pocket far from the expected kinase/ligase catalytic site, specifically recognizes the cytosine and ribose portions of the product inhibitor. {ECO:0000305\|PubMed:16216072}.
Similarity:		Belongs to the CTP synthase family. {ECO:0000255\|HAMAP- Rule:MF_01227}.