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1em8
From Proteopedia
(New page: 200px<br /><applet load="1em8" size="450" color="white" frame="true" align="right" spinBox="true" caption="1em8, resolution 2.1Å" /> '''Crystal structure of ...) |
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| - | [[Image:1em8.gif|left|200px]]<br /><applet load="1em8" size=" | + | [[Image:1em8.gif|left|200px]]<br /><applet load="1em8" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1em8, resolution 2.1Å" /> | caption="1em8, resolution 2.1Å" /> | ||
'''Crystal structure of chi and psi subunit heterodimer from DNA POL III'''<br /> | '''Crystal structure of chi and psi subunit heterodimer from DNA POL III'''<br /> | ||
==Overview== | ==Overview== | ||
| - | The chi (chi) and psi (psi) subunits of Escherichia coli DNA polymerase | + | 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. |
==About this Structure== | ==About this Structure== | ||
| - | 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:// | + | 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://oca.weizmann.ac.il/oca-bin/ocashort?id=1EM8 OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Escherichia coli]] | [[Category: Escherichia coli]] | ||
[[Category: Protein complex]] | [[Category: Protein complex]] | ||
| - | [[Category: Donnell, M | + | [[Category: Donnell, M O.]] |
[[Category: Finkelstein, J.]] | [[Category: Finkelstein, J.]] | ||
| - | [[Category: Gulbis, J | + | [[Category: Gulbis, J M.]] |
[[Category: Kuriyan, J.]] | [[Category: Kuriyan, J.]] | ||
[[Category: alpha-beta fold]] | [[Category: alpha-beta fold]] | ||
| Line 23: | Line 23: | ||
[[Category: heterodimer]] | [[Category: heterodimer]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:29:15 2008'' |
Revision as of 10:29, 21 February 2008
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Crystal structure of chi and psi subunit heterodimer from DNA POL III
Overview
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.
About this Structure
1EM8 is a Protein complex structure of sequences from Escherichia coli. Active as DNA-directed DNA polymerase, with EC number 2.7.7.7 Full crystallographic information is available from OCA.
Reference
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:14717711
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