1s1m
From Proteopedia
(New page: 200px<br /><applet load="1s1m" size="450" color="white" frame="true" align="right" spinBox="true" caption="1s1m, resolution 2.30Å" /> '''Crystal Structure of...) |
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| - | [[Image:1s1m.jpg|left|200px]]<br /><applet load="1s1m" size=" | + | [[Image:1s1m.jpg|left|200px]]<br /><applet load="1s1m" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1s1m, resolution 2.30Å" /> | caption="1s1m, resolution 2.30Å" /> | ||
'''Crystal Structure of E. Coli CTP Synthetase'''<br /> | '''Crystal Structure of E. Coli CTP Synthetase'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Cytidine triphosphate synthetases (CTPSs) produce CTP from UTP and | + | Cytidine triphosphate synthetases (CTPSs) produce CTP from UTP and glutamine, and regulate intracellular CTP levels through interactions with the four ribonucleotide triphosphates. We solved the 2.3-A resolution crystal structure of Escherichia coli CTPS using Hg-MAD phasing. The structure reveals a nearly symmetric 222 tetramer, in which each bifunctional monomer contains a dethiobiotin synthetase-like amidoligase N-terminal domain and a Type 1 glutamine amidotransferase C-terminal domain. For each amidoligase active site, essential ATP- and UTP-binding surfaces are contributed by three monomers, suggesting that activity requires tetramer formation, and that a nucleotide-dependent dimer-tetramer equilibrium contributes to the observed positive cooperativity. A gated channel that spans 25 A 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. Guanine nucleotide binding sites of structurally related GTPases superimpose on this cleft, providing insights into allosteric regulation by GTP. Mutations that confer nucleoside drug resistance and release CTP inhibition map to a pocket that neighbors the UTP-binding site and can accommodate a pyrimidine ring. Its location suggests that competitive feedback inhibition is affected via a distinct product/drug binding site that overlaps the substrate triphosphate binding site. Overall, the E. coli structure provides a framework for homology modeling of other CTPSs and structure-based design of anti-CTPS therapeutics. |
==About this Structure== | ==About this Structure== | ||
| - | 1S1M is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with SO4, MG, IOD and MPD as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/CTP_synthase CTP synthase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=6.3.4.2 6.3.4.2] Full crystallographic information is available from [http:// | + | 1S1M is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with <scene name='pdbligand=SO4:'>SO4</scene>, <scene name='pdbligand=MG:'>MG</scene>, <scene name='pdbligand=IOD:'>IOD</scene> and <scene name='pdbligand=MPD:'>MPD</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/CTP_synthase CTP synthase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=6.3.4.2 6.3.4.2] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1S1M OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Escherichia coli]] | [[Category: Escherichia coli]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Anderson, P | + | [[Category: Anderson, P M.]] |
| - | [[Category: Baldwin, E | + | [[Category: Baldwin, E P.]] |
| - | [[Category: Endrizzi, J | + | [[Category: Endrizzi, J A.]] |
[[Category: Kim, H.]] | [[Category: Kim, H.]] | ||
[[Category: IOD]] | [[Category: IOD]] | ||
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[[Category: utp:ammonia ligase (adp-forming)]] | [[Category: utp:ammonia ligase (adp-forming)]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 14:56:56 2008'' |
Revision as of 12:56, 21 February 2008
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Crystal Structure of E. Coli CTP Synthetase
Overview
Cytidine triphosphate synthetases (CTPSs) produce CTP from UTP and glutamine, and regulate intracellular CTP levels through interactions with the four ribonucleotide triphosphates. We solved the 2.3-A resolution crystal structure of Escherichia coli CTPS using Hg-MAD phasing. The structure reveals a nearly symmetric 222 tetramer, in which each bifunctional monomer contains a dethiobiotin synthetase-like amidoligase N-terminal domain and a Type 1 glutamine amidotransferase C-terminal domain. For each amidoligase active site, essential ATP- and UTP-binding surfaces are contributed by three monomers, suggesting that activity requires tetramer formation, and that a nucleotide-dependent dimer-tetramer equilibrium contributes to the observed positive cooperativity. A gated channel that spans 25 A 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. Guanine nucleotide binding sites of structurally related GTPases superimpose on this cleft, providing insights into allosteric regulation by GTP. Mutations that confer nucleoside drug resistance and release CTP inhibition map to a pocket that neighbors the UTP-binding site and can accommodate a pyrimidine ring. Its location suggests that competitive feedback inhibition is affected via a distinct product/drug binding site that overlaps the substrate triphosphate binding site. Overall, the E. coli structure provides a framework for homology modeling of other CTPSs and structure-based design of anti-CTPS therapeutics.
About this Structure
1S1M is a Single protein structure of sequence from Escherichia coli with , , and as ligands. Active as CTP synthase, with EC number 6.3.4.2 Full crystallographic information is available from OCA.
Reference
Crystal structure of Escherichia coli cytidine triphosphate synthetase, a nucleotide-regulated glutamine amidotransferase/ATP-dependent amidoligase fusion protein and homologue of anticancer and antiparasitic drug targets., Endrizzi JA, Kim H, Anderson PM, Baldwin EP, Biochemistry. 2004 Jun 1;43(21):6447-63. PMID:15157079
Page seeded by OCA on Thu Feb 21 14:56:56 2008
Categories: CTP synthase | Escherichia coli | Single protein | Anderson, P M. | Baldwin, E P. | Endrizzi, J A. | Kim, H. | IOD | MG | MPD | SO4 | Ammonia lyase | Ammonia tunnel | Class-ii glutamine amidotransferase | Ctp synthetase | Cytidine 5'-triphosphate synthase | Utp:ammonia ligase (adp-forming)
