tailieunhanh - Báo cáo khóa học: Crystal structure of the chi:psi subassembly of the Escherichia coli DNA polymerase clamp-loader complex

The chi (v)and psi(w) subunits of Escherichia coliDNA polymerase III formaheterodimer that is associatedwith the ATP-dependent clamp-loadermachinery. InE. coli,thev:w heterodimer serves as a bridge between the clamp-loader complex and the single-strandedDNA-binding protein. We determined the crystal structure of thev:wheterodimer at A ˚ resolution. Although neitherv(147 residues) nor w (137 residues) bind to nucleotides, the fold of each protein is similar to the folds of mononucleotide-(v) or dinucleotide-(w) binding proteins, without marked similarity to the structures of the clamp-loader subunits | Eur. J. Biochem. 271 439-449 2004 FEBS 2004 doi Crystal structure of the chi psi subassembly of the Escherichia coli DNA polymerase clamp-loader complex Jacqueline M. Gulbis1 I Steven L. Kazmirski2 3 Jeff Finkelstein4 Zvi Kelman4 f Mike O Donnell4 and John Kuriyan2 3 1 Laboratory of Molecular Biophysics and Laboratory of DNA Replication Howard Hughes Medical Institute The Rockefeller University New York NY USA department of Molecular and Cell Biology and of Chemistry University of California Berkeley CA USA 3Physical Biosciences Division Lawrence Berkeley National Laboratory Berkeley CA USA The chi v and psi w subunits of Escherichia coli DNA polymerase III form a heterodimer that is associated with the ATP-dependent clamp-loader machinery. In E. coli the v w heterodimer serves as a bridge between the clamp-loader complex and the single-stranded DNA-binding protein. We determined the crystal structure of the v w heterodimer at Ay resolution. Although neither v 147 residues nor w 137 residues bind to nucleotides the fold of each protein is similar to the folds of mononucleotide- v or dinucleotide- W binding proteins without marked similarity to the structures of the clamp-loader subunits. Genes encoding v and w proteins are found to be readily identifiable in several bacterial genomes and sequence alignments showed that residues at the v W 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 v W complex. One of the conserved regions was found to be located on v distal to the w 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 w 26 residues that is disordered in the crystal .