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| [[Image:1em8.gif|left|200px]]<br /><applet load="1em8" size="450" color="white" frame="true" align="right" spinBox="true"
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| caption="1em8, resolution 2.1Å" />
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| '''Crystal structure of chi and psi subunit heterodimer from DNA POL III'''<br />
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| ==Overview== | | ==Crystal structure of chi and psi subunit heterodimer from DNA POL III== |
| The chi (chi) and psi (psi) subunits of Escherichia coli DNA polymerase, III form a heterodimer that is associated with the ATP-dependent, clamp-loader machinery. In E. coli, the chi:psi heterodimer serves as a, bridge between the clamp-loader complex and the single-stranded, DNA-binding protein. We determined the crystal structure of the chi:psi, heterodimer at 2.1 A resolution. Although neither chi (147 residues) nor, psi (137 residues) bind to nucleotides, the fold of each protein is, similar to the folds of mononucleotide-(chi) or dinucleotide-(psi) binding, proteins, without marked similarity to the structures of the clamp-loader, subunits. Genes encoding chi and psi proteins are found to be readily, identifiable in several bacterial genomes and sequence alignments showed, that residues at the chi:psi interface are highly conserved in both, proteins, suggesting that the heterodimeric interaction is of functional, significance. The conservation of surface-exposed residues is restricted, to the interfacial region and to just two other regions in the chi:psi, complex. One of the conserved regions was found to be located on chi, distal to the psi interaction region, and we identified this as the, binding site for a C-terminal segment of the single-stranded DNA-binding, protein. The other region of sequence conservation is localized to an, N-terminal segment of psi (26 residues) that is disordered in the crystal, structure. We speculate that psi is linked to the clamp-loader complex by, this flexible, but conserved, N-terminal segment, and that the chi:psi, unit is linked to the single-stranded DNA-binding protein via the distal, surface of chi. The base of the clamp-loader complex has an open C-shaped, structure, and the shape of the chi:psi complex is suggestive of a loose, docking within the crevice formed by the open faces of the delta and, delta' subunits of the clamp-loader.
| | <StructureSection load='1em8' size='340' side='right'caption='[[1em8]], [[Resolution|resolution]] 2.10Å' scene=''> |
| | == Structural highlights == |
| | <table><tr><td colspan='2'>[[1em8]] is a 4 chain structure with sequence from [https://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1EM8 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1EM8 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]] 2.1Å</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=1em8 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1em8 OCA], [https://pdbe.org/1em8 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1em8 RCSB], [https://www.ebi.ac.uk/pdbsum/1em8 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1em8 ProSAT]</span></td></tr> |
| | </table> |
| | == Function == |
| | [https://www.uniprot.org/uniprot/HOLC_ECOLI HOLC_ECOLI] DNA polymerase III is a complex, multichain enzyme responsible for most of the replicative synthesis in bacteria. This DNA polymerase also exhibits 3' to 5' exonuclease activity. |
| | == 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/em/1em8_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=1em8 ConSurf]. |
| | <div style="clear:both"></div> |
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| ==About this Structure== | | ==See Also== |
| 1EM8 is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Active as [http://en.wikipedia.org/wiki/DNA-directed_DNA_polymerase DNA-directed DNA polymerase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.7.7.7 2.7.7.7] Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1EM8 OCA].
| | *[[DNA polymerase 3D structures|DNA polymerase 3D structures]] |
| | | __TOC__ |
| ==Reference==
| | </StructureSection> |
| Crystal structure of the chi:psi sub-assembly of the Escherichia coli DNA polymerase clamp-loader complex., Gulbis JM, Kazmirski SL, Finkelstein J, Kelman Z, O'Donnell M, Kuriyan J, Eur J Biochem. 2004 Jan;271(2):439-49. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=14717711 14717711]
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| [[Category: DNA-directed DNA polymerase]]
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| [[Category: Escherichia coli]] | | [[Category: Escherichia coli]] |
| [[Category: Protein complex]] | | [[Category: Large Structures]] |
| [[Category: Donnell, M.O.]]
| | [[Category: Finkelstein J]] |
| [[Category: Finkelstein, J.]] | | [[Category: Gulbis JM]] |
| [[Category: Gulbis, J.M.]] | | [[Category: Kuriyan J]] |
| [[Category: Kuriyan, J.]] | | [[Category: O'Donnell M]] |
| [[Category: alpha-beta fold]] | |
| [[Category: clamp-loader]]
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| [[Category: dna pol iii]]
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| [[Category: heterodimer]]
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| ''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Tue Nov 20 14:07:20 2007''
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