View source for 5cfg


==C2 crystal form of APE1 with Mg2+==
<StructureSection load='5cfg' size='340' side='right'caption='[[5cfg]], [[Resolution|resolution]] 1.80&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[5cfg]] 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=5CFG OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=5CFG 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]] 1.8&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=MG:MAGNESIUM+ION'>MG</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=5cfg FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=5cfg OCA], [https://pdbe.org/5cfg PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=5cfg RCSB], [https://www.ebi.ac.uk/pdbsum/5cfg PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=5cfg 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 ==
Oxidatively damaged DNA bases are substrates for two overlapping repair pathways: DNA glycosylase-initiated base excision repair (BER) and apurinic/apyrimidinic (AP) endonuclease-initiated nucleotide incision repair (NIR). In the BER pathway, an AP endonuclease cleaves DNA at AP sites and 3'-blocking moieties generated by DNA glycosylases, whereas in the NIR pathway, the same AP endonuclease incises DNA 5' to an oxidized base. The majority of characterized AP endonucleases possess classic BER activities, and approximately a half of them can also have a NIR activity. At present, the molecular mechanism underlying DNA substrate specificity of AP endonucleases remains unclear mainly due to the absence of a published structure of the enzyme in complex with a damaged base. To identify critical residues involved in the NIR function, we performed biochemical and structural characterization of Bacillus subtilis AP endonuclease ExoA and compared its crystal structure with the structures of other AP endonucleases: Escherichiacoli exonuclease III (Xth), human APE1, and archaeal Mth212. We found conserved amino acid residues in the NIR-specific enzymes APE1, Mth212, and ExoA. Four of these positions were studied by means of point mutations in APE1: we applied substitution with the corresponding residue found in NIR-deficient E. coli Xth (Y128H, N174Q, G231S, and T268D). The APE1-T268D mutant showed a drastically decreased NIR activity and an inverted Mg2+ dependence of the AP site cleavage activity, which is in line with the presence of an aspartic residue at the equivalent position among other known NIR-deficient AP endonucleases. Taken together, these data show that NIR is an evolutionarily conserved function in the Xth family of AP endonucleases.

Structural comparison of AP endonucleases from the exonuclease III family reveals new amino acid residues in human AP endonuclease 1 that are involved in incision of damaged DNA.,Redrejo-Rodriguez M, Vigouroux A, Mursalimov A, Grin I, Alili D, Koshenov Z, Akishev Z, Maksimenko A, Bissenbaev AK, Matkarimov BT, Saparbaev M, Ishchenko AA, Morera S Biochimie. 2016 Jun 22. pii: S0300-9084(16)30120-1. doi:, 10.1016/j.biochi.2016.06.011. PMID:27343627<ref>PMID:27343627</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 5cfg" 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/>
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</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Morera S]]
[[Category: Vigouroux A]]