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J. Biol. Chem., Vol. 277, Issue 16, 13401-13408, April 19, 2002

This Article Full Text Full Text (PDF) All Versions of this Article: 277/16/13401    most recent M110833200v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Bullard, J. M. Articles by McHenry, C. S. Search for Related Content PubMed PubMed Citation Articles by Bullard, J. M. Articles by McHenry, C. S.

DNA Polymerase III Holoenzyme from Thermus thermophilus Identification, Expression, Purification of Components, and Use to Reconstitute a Processive Replicase^*

James M. Bullard, Jennifer C. Williams, Wendy K. Acker, Carsten Jacobi^§, Nebojsa Janjic, and Charles S. McHenry^¶

From  Replidyne, Inc., Denver, Colorado 80206, the ^§ Institute of Microbiology and Genetics, University of Göttingen, Göttingen, Germany, and the ^¶ Department of Biochemistry and Molecular Genetics, University of Colorado Health Sciences Center, Denver, Colorado 80262

DNA replication in bacteria is performed by a specialized multicomponent replicase, the DNA polymerase III holoenzyme, that consist of three essential components: a polymerase, the  sliding clamp processivity factor, and the DnaX complex clamp-loader. We report here the assembly of the minimal functional holoenzyme from Thermus thermophilus (Tth), an extreme thermophile. The minimal holoenzyme consists of  (pol III catalytic subunit),  (sliding clamp processivity factor), and the essential DnaX (/),  and ' components of the DnaX complex. We show with purified recombinant proteins that these five components are required for rapid and processive DNA synthesis on long single-stranded DNA templates. Subunit interactions known to occur in DNA polymerase III holoenzyme from mesophilic bacteria including -' interaction, '-/ complex formation, and - interaction, also occur within the Tth enzyme. As in mesophilic holoenzymes, in the presence of a primed DNA template, these subunits assemble into a stable initiation complex in an ATP-dependent manner. However, in contrast to replicative polymerases from mesophilic bacteria, Tth holoenzyme is efficient only at temperatures above 50 °C, both with regard to initiation complex formation and processive DNA synthesis. The minimal Tth DNA polymerase III holoenzyme displays an elongation rate of 350 bp/s at 72 °C and a processivity of greater than 8.6 kilobases, the length of the template that is fully replicated after a single association event.

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