View source for 6hpt


==Crystal structure of human Pif1 helicase, apoform.==
<StructureSection load='6hpt' size='340' side='right'caption='[[6hpt]], [[Resolution|resolution]] 1.44&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[6hpt]] 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=6HPT OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=6HPT 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]] 1.44&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=SO4:SULFATE+ION'>SO4</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=6hpt FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=6hpt OCA], [https://pdbe.org/6hpt PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=6hpt RCSB], [https://www.ebi.ac.uk/pdbsum/6hpt PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=6hpt ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/PIF1_HUMAN PIF1_HUMAN] DNA-dependent ATPase and 5'-3' DNA helicase required for the maintenance of both mitochondrial and nuclear genome stability. Efficiently unwinds G-quadruplex (G4) DNA structures and forked RNA-DNA hybrids. Resolves G4 structures, preventing replication pausing and double-strand breaks (DSBs) at G4 motifs. Involved in the maintenance of telomeric DNA. Inhibits telomere elongation, de novo telomere formation and telomere addition to DSBs via catalytic inhibition of telomerase. Reduces the processivity of telomerase by displacing active telomerase from DNA ends. Releases telomerase by unwinding the short telomerase RNA/telomeric DNA hybrid that is the intermediate in the telomerase reaction. Possesses an intrinsic strand annealing activity.[HAMAP-Rule:MF_03176]<ref>PMID:16522649</ref> <ref>PMID:17172855</ref> <ref>PMID:17827721</ref> <ref>PMID:18835853</ref> <ref>PMID:19700773</ref> <ref>PMID:20524933</ref> <ref>PMID:23657261</ref> 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Pif1 is a multifunctional helicase and DNA processing enzyme that has roles in genome stability. The enzyme is conserved in eukaryotes and also found in some prokaryotes. The functions of human PIF1 (hPIF1) are also critical for survival of certain tumour cell lines during replication stress, making it an important target for cancer therapy. Crystal structures of hPIF1 presented here explore structural events along the chemical reaction coordinate of ATP hydrolysis at an unprecedented level of detail. The structures for the apo as well as the ground and transition states reveal conformational adjustments in defined protein segments that can trigger larger domain movements required for helicase action. Comparisons with the structures of yeast and bacterial Pif1 reveal a conserved ssDNA binding channel in hPIF1 that we show is critical for single-stranded DNA binding during unwinding, but not the binding of G quadruplex DNA. Mutational analysis suggests that while the ssDNA-binding channel is important for helicase activity, it is not used in DNA annealing. Structural differences, in particular in the DNA strand separation wedge region, highlight significant evolutionary divergence of the human PIF1 protein from bacterial and yeast orthologues.

Structural and functional analysis of the nucleotide and DNA binding activities of the human PIF1 helicase.,Dehghani-Tafti S, Levdikov V, Antson AA, Bax B, Sanders CM Nucleic Acids Res. 2019 Jan 30. pii: 5304331. doi: 10.1093/nar/gkz028. PMID:30698796<ref>PMID:30698796</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 6hpt" style="background-color:#fffaf0;"></div>

==See Also==
*[[Helicase 3D structures|Helicase 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Antson AA]]
[[Category: Bax BD]]
[[Category: Dehghani-Tafti S]]
[[Category: Levdikov VM]]
[[Category: Sanders CM]]