1xxi
ADP Bound E. coli Clamp Loader Complex
Structural highlights
FunctionDPO3X_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. Isoform tau: serves as a scaffold to help in the dimerization of the core complex. Isoform gamma: seems to interact with the delta subunit. to transfer the beta subunit on the DNA. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedClamp-loader complexes are heteropentameric AAA+ ATPases that load sliding clamps onto DNA. The structure of the nucleotide-free Escherichia coli clamp loader had been determined previously and led to the proposal that the clamp-loader cycles between an inactive state, in which the ATPase domains form a closed ring, and an active state that opens up to form a "C" shape. The crystal structure was interpreted as being closer to the active state than the inactive state. The crystal structure of a nucleotide-bound eukaryotic clamp loader [replication factor C (RFC)] revealed a different and more tightly packed spiral organization of the ATPase domains, raising questions about the significance of the conformation seen earlier for the bacterial clamp loader. We describe crystal structures of the E. coli clamp-loader complex bound to the ATP analog ATPgammaS (at a resolution of 3.5 A) and ADP (at a resolution of 4.1 A). These structures are similar to that of the nucleotide-free clamp-loader complex. Only two of the three functional ATP-binding sites are occupied by ATPgammaS or ADP in these structures, and the bound nucleotides make no interfacial contacts in the complex. These results, along with data from isothermal titration calorimetry, molecular dynamics simulations, and comparison with the RFC structure, suggest that the more open form of the E. coli clamp loader described earlier and in the present work corresponds to a stable inactive state of the clamp loader in which the ATPase domains are prevented from engaging the clamp in the highly cooperative manner seen in the fully ATP-loaded RFC-clamp structure. Structural analysis of the inactive state of the Escherichia coli DNA polymerase clamp-loader complex.,Kazmirski SL, Podobnik M, Weitze TF, O'Donnell M, Kuriyan J Proc Natl Acad Sci U S A. 2004 Nov 30;101(48):16750-5. Epub 2004 Nov 19. PMID:15556993[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences | ||||||||||||||||||||
