View source for 5wn4


==APE1 exonuclease substrate complex with a C/T mismatch==
<StructureSection load='5wn4' size='340' side='right'caption='[[5wn4]], [[Resolution|resolution]] 2.10&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[5wn4]] is a 5 chain structure with sequence from [https://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] and [https://en.wikipedia.org/wiki/Synthetic_construct Synthetic construct]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=5WN4 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=5WN4 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]] 2.1&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=C7R:2-DEOXY-5-O-THIOPHOSPHONOCYTIDINE'>C7R</scene>, <scene name='pdbligand=CA:CALCIUM+ION'>CA</scene>, <scene name='pdbligand=CL:CHLORIDE+ION'>CL</scene>, <scene name='pdbligand=EDO:1,2-ETHANEDIOL'>EDO</scene>, <scene name='pdbligand=NA:SODIUM+ION'>NA</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=5wn4 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=5wn4 OCA], [https://pdbe.org/5wn4 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=5wn4 RCSB], [https://www.ebi.ac.uk/pdbsum/5wn4 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=5wn4 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/APEX1_HUMAN APEX1_HUMAN] Multifunctional protein that plays a central role in the cellular response to oxidative stress. The two major activities of APEX1 in DNA repair and redox regulation of transcriptional factors. Functions as a apurinic/apyrimidinic (AP) endodeoxyribonuclease in the DNA base excision repair (BER) pathway of DNA lesions induced by oxidative and alkylating agents. Initiates repair of AP sites in DNA by catalyzing hydrolytic incision of the phosphodiester backbone immediately adjacent to the damage, generating a single-strand break with 5'-deoxyribose phosphate and 3'-hydroxyl ends. Does also incise at AP sites in the DNA strand of DNA/RNA hybrids, single-stranded DNA regions of R-loop structures, and single-stranded RNA molecules. Has a 3'-5' exoribonuclease activity on mismatched deoxyribonucleotides at the 3' termini of nicked or gapped DNA molecules during short-patch BER. Possesses a DNA 3' phosphodiesterase activity capable of removing lesions (such as phosphoglycolate) blocking the 3' side of DNA strand breaks. May also play a role in the epigenetic regulation of gene expression by participating in DNA demethylation. Acts as a loading factor for POLB onto non-incised AP sites in DNA and stimulates the 5'-terminal deoxyribose 5'-phosphate (dRp) excision activity of POLB. Plays a role in the protection from granzymes-mediated cellular repair leading to cell death. Also involved in the DNA cleavage step of class switch recombination (CSR). On the other hand, APEX1 also exerts reversible nuclear redox activity to regulate DNA binding affinity and transcriptional activity of transcriptional factors by controlling the redox status of their DNA-binding domain, such as the FOS/JUN AP-1 complex after exposure to IR. Involved in calcium-dependent down-regulation of parathyroid hormone (PTH) expression by binding to negative calcium response elements (nCaREs). Together with HNRNPL or the dimer XRCC5/XRCC6, associates with nCaRE, acting as an activator of transcriptional repression. Stimulates the YBX1-mediated MDR1 promoter activity, when acetylated at Lys-6 and Lys-7, leading to drug resistance. Acts also as an endoribonuclease involved in the control of single-stranded RNA metabolism. Plays a role in regulating MYC mRNA turnover by preferentially cleaving in between UA and CA dinucleotides of the MYC coding region determinant (CRD). In association with NMD1, plays a role in the rRNA quality control process during cell cycle progression. Associates, together with YBX1, on the MDR1 promoter. Together with NPM1, associates with rRNA. Binds DNA and RNA.<ref>PMID:1719477</ref> <ref>PMID:12524539</ref> <ref>PMID:8355688</ref> <ref>PMID:8621488</ref> <ref>PMID:8932375</ref> <ref>PMID:9108029</ref> <ref>PMID:9207062</ref> <ref>PMID:9804799</ref> <ref>PMID:9560228</ref> <ref>PMID:10023679</ref> <ref>PMID:11118054</ref> <ref>PMID:11452037</ref> <ref>PMID:11832948</ref> <ref>PMID:11809897</ref> <ref>PMID:16617147</ref> <ref>PMID:18439621</ref> <ref>PMID:18809583</ref> <ref>PMID:18179823</ref> <ref>PMID:18579163</ref> <ref>PMID:19188445</ref> <ref>PMID:19401441</ref> <ref>PMID:19934257</ref> <ref>PMID:20699270</ref> <ref>PMID:21496894</ref> <ref>PMID:21762700</ref> 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Human apurinic/apyrimidinic (AP) endonuclease 1 (APE1) is an essential DNA repair enzyme which uses a single active site to process DNA damage via two distinct activities: (1) AP-endonuclease and (2) 3' to 5' exonuclease. The AP-endonuclease activity cleaves at AP-sites, while the exonuclease activity excises bulkier 3' mismatches and DNA damage to generate clean DNA ends suitable for downstream repair. Molecular details of the exonuclease reaction and how one active site can accommodate various toxic DNA repair intermediates remains elusive despite being biologically important. Here, we report multiple high-resolution APE1-DNA structural snapshots revealing how APE1 removes 3' mismatches and DNA damage by placing the 3' group within the intra-helical DNA cavity via a non-base flipping mechanism. This process is facilitated by a DNA nick, instability of a mismatched/damaged base, and bending of the DNA. These results illustrate how APE1 cleanses DNA dirty-ends to generate suitable substrates for downstream repair enzymes.

Molecular snapshots of APE1 proofreading mismatches and removing DNA damage.,Whitaker AM, Flynn TS, Freudenthal BD Nat Commun. 2018 Jan 26;9(1):399. doi: 10.1038/s41467-017-02175-y. PMID:29374164<ref>PMID:29374164</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 5wn4" style="background-color:#fffaf0;"></div>

==See Also==
*[[Apurinic/apyrimidinic endonuclease 3D structures|Apurinic/apyrimidinic endonuclease 3D structures]]
*[[Endonuclease 3D structures|Endonuclease 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Synthetic construct]]
[[Category: Freudenthal BD]]
[[Category: Whitaker AM]]