View source for 2qhn


==Crystal Structure of Chek1 in Complex with Inhibitor 1a==
<StructureSection load='2qhn' size='340' side='right'caption='[[2qhn]], [[Resolution|resolution]] 1.70&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[2qhn]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2QHN OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=2QHN FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 1.7&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=582:5-ETHYL-3-METHYL-1,5-DIHYDRO-4H-PYRAZOLO[4,3-C]QUINOLIN-4-ONE'>582</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=2qhn FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=2qhn OCA], [https://pdbe.org/2qhn PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=2qhn RCSB], [https://www.ebi.ac.uk/pdbsum/2qhn PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=2qhn ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/CHK1_HUMAN CHK1_HUMAN] Serine/threonine-protein kinase which is required for checkpoint-mediated cell cycle arrest and activation of DNA repair in response to the presence of DNA damage or unreplicated DNA. May also negatively regulate cell cycle progression during unperturbed cell cycles. This regulation is achieved by a number of mechanisms that together help to preserve the integrity of the genome. Recognizes the substrate consensus sequence [R-X-X-S/T]. Binds to and phosphorylates CDC25A, CDC25B and CDC25C. Phosphorylation of CDC25A at 'Ser-178' and 'Thr-507' and phosphorylation of CDC25C at 'Ser-216' creates binding sites for 14-3-3 proteins which inhibit CDC25A and CDC25C. Phosphorylation of CDC25A at 'Ser-76', 'Ser-124', 'Ser-178', 'Ser-279' and 'Ser-293' promotes proteolysis of CDC25A. Phosphorylation of CDC25A at 'Ser-76' primes the protein for subsequent phosphorylation at 'Ser-79', 'Ser-82' and 'Ser-88' by NEK11, which is required for polyubiquitination and degradation of CDCD25A. Inhibition of CDC25 leads to increased inhibitory tyrosine phosphorylation of CDK-cyclin complexes and blocks cell cycle progression. Also phosphorylates NEK6. Binds to and phosphorylates RAD51 at 'Thr-309', which promotes the release of RAD51 from BRCA2 and enhances the association of RAD51 with chromatin, thereby promoting DNA repair by homologous recombination. Phosphorylates multiple sites within the C-terminus of TP53, which promotes activation of TP53 by acetylation and promotes cell cycle arrest and suppression of cellular proliferation. Also promotes repair of DNA cross-links through phosphorylation of FANCE. Binds to and phosphorylates TLK1 at 'Ser-743', which prevents the TLK1-dependent phosphorylation of the chromatin assembly factor ASF1A. This may enhance chromatin assembly both in the presence or absence of DNA damage. May also play a role in replication fork maintenance through regulation of PCNA. May regulate the transcription of genes that regulate cell-cycle progression through the phosphorylation of histones. Phosphorylates histone H3.1 (to form H3T11ph), which leads to epigenetic inhibition of a subset of genes. May also phosphorylate RB1 to promote its interaction with the E2F family of transcription factors and subsequent cell cycle arrest.<ref>PMID:9278511</ref> <ref>PMID:10673501</ref> <ref>PMID:11535615</ref> <ref>PMID:12446774</ref> <ref>PMID:12399544</ref> <ref>PMID:12676583</ref> <ref>PMID:12660173</ref> <ref>PMID:14681206</ref> <ref>PMID:12676925</ref> <ref>PMID:12759351</ref> <ref>PMID:14559997</ref> <ref>PMID:14988723</ref> <ref>PMID:15311285</ref> <ref>PMID:15659650</ref> <ref>PMID:15665856</ref> <ref>PMID:15650047</ref> <ref>PMID:16511572</ref> <ref>PMID:16963448</ref> <ref>PMID:17380128</ref> <ref>PMID:17296736</ref> <ref>PMID:18510930</ref> <ref>PMID:18728393</ref> <ref>PMID:18451105</ref> <ref>PMID:18317453</ref> <ref>PMID:19734889</ref> <ref>PMID:20090422</ref>   Isoform 2: Endogenous repressor of isoform 1, interacts with, and antagonizes CHK1 to promote the S to G2/M phase transition.<ref>PMID:9278511</ref> <ref>PMID:10673501</ref> <ref>PMID:11535615</ref> <ref>PMID:12446774</ref> <ref>PMID:12399544</ref> <ref>PMID:12676583</ref> <ref>PMID:12660173</ref> <ref>PMID:14681206</ref> <ref>PMID:12676925</ref> <ref>PMID:12759351</ref> <ref>PMID:14559997</ref> <ref>PMID:14988723</ref> <ref>PMID:15311285</ref> <ref>PMID:15659650</ref> <ref>PMID:15665856</ref> <ref>PMID:15650047</ref> <ref>PMID:16511572</ref> <ref>PMID:16963448</ref> <ref>PMID:17380128</ref> <ref>PMID:17296736</ref> <ref>PMID:18510930</ref> <ref>PMID:18728393</ref> <ref>PMID:18451105</ref> <ref>PMID:18317453</ref> <ref>PMID:19734889</ref> <ref>PMID:20090422</ref> 
== Evolutionary Conservation ==
[[Image:Consurf_key_small.gif|200px|right]]
Check<jmol>
  <jmolCheckbox>
    <scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/qh/2qhn_consurf.spt"</scriptWhenChecked>
    <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview01.spt</scriptWhenUnchecked>
    <text>to colour the structure by Evolutionary Conservation</text>
  </jmolCheckbox>
</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/main_output.php?pdb_ID=2qhn ConSurf].
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== Publication Abstract from PubMed ==
The development of 2,5-dihydro-4H-pyrazolo[4,3-c]quinolin-4-ones as inhibitors of Chk1 kinase is described. Introduction of a fused ring at the C7/C8 positions of the pyrazoloquinolinone provided an increase in potency while guidance from overlapping inhibitor bound Chk1 X-ray crystal structures contributed to the discovery of a potent and solubilizing propyl amine moiety in compound 52 (Chk1 IC(50)=3.1 nM).

Optimization of a pyrazoloquinolinone class of Chk1 kinase inhibitors.,Brnardic EJ, Garbaccio RM, Fraley ME, Tasber ES, Steen JT, Arrington KL, Dudkin VY, Hartman GD, Stirdivant SM, Drakas BA, Rickert K, Walsh ES, Hamilton K, Buser CA, Hardwick J, Tao W, Beck SC, Mao X, Lobell RB, Sepp-Lorenzino L, Yan Y, Ikuta M, Munshi SK, Kuo LC, Kreatsoulas C Bioorg Med Chem Lett. 2007 Nov 1;17(21):5989-94. Epub 2007 Aug 19. PMID:17804227<ref>PMID:17804227</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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<div class="pdbe-citations 2qhn" style="background-color:#fffaf0;"></div>

==See Also==
*[[Serine/threonine protein kinase 3D structures|Serine/threonine protein kinase 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Munshi S]]
[[Category: Yan Y]]