Devoted to the lagging strand - The χ subunit of DNA polymerase III holoenzyme contacts SSB to promote processive elongation and sliding clamp assembly Journal Article
| Authors: | Kelman, Z.; Yuzhakov, A.; Andjelkovic, J.; O'Donnell, M. |
| Article Title: | Devoted to the lagging strand - The χ subunit of DNA polymerase III holoenzyme contacts SSB to promote processive elongation and sliding clamp assembly |
| Abstract: | Escherichia coli DNA polymerase III holoenzyme contains 10 different subunits which assort into three functional components: a core catalytic unit containing DNA polymerase activity, the β sliding clamp that encircles DNA for processive replication, and a multi-subunit clamp loader apparatus called γ complex that uses ATP to assemble the β clamp onto DNA. We examine here the function of the χ subunit of the γ complex clamp loader. Omission of χ from the holoenzyme prevents contact with single-stranded DNA-binding protein (SSB) and lowers the efficiency of clamp loading and chain elongation under conditions of elevated salt. We also show that the product of a classic point mutant of SSB, SSB-113, lacks strong affinity for χ and is defective in promoting clamp loading and processive replication at elevated ionic strength, SSB-113 carries a single amino acid replacement at the penultimate residue of the C-terminus, indicating the C-terminus as a site of interaction with χ. Indeed, a peptide of the 15 C-terminal residues of SSB is sufficient to bind to χ. These results establish a role for the χ subunit in contacting SSB, thus enhancing the clamp loading and processivity of synthesis of the holoenzyme, presumably by helping to localize the holoenzyme to sites of SSB-coated ssDNA. |
| Keywords: | controlled study; unclassified drug; dna binding protein; dna-binding proteins; nonhuman; dna polymerase; dna replication; dna synthesis; amino acid substitution; carboxy terminal sequence; protein assembly; protein protein interaction; enzyme activity; bacteria (microorganisms); dna; escherichia coli; rna translation; binding sites; adenosine triphosphate; dna, single-stranded; point mutation; enzyme subunit; sodium chloride; enzyme synthesis; enzyme active site; coenzymes; bacterial enzyme; dna directed dna polymerase gamma; holoenzyme; ionic strength; osmolar concentration; dna polymerase iii; priority journal; article; peptide chain elongation, translational; dna polymerase iii holoenzyme; clamp loader; ssb; ssb-113 |
| Journal Title: | EMBO Journal |
| Volume: | 17 |
| Issue: | 8 |
| ISSN: | 0261-4189 |
| Publisher: | Wiley Blackwell |
| Date Published: | 1998-04-15 |
| Start Page: | 2436 |
| End Page: | 2449 |
| Language: | English |
| DOI: | 10.1093/emboj/17.8.2436 |
| PUBMED: | 9545254 |
| PROVIDER: | scopus |
| PMCID: | PMC1170586 |
| DOI/URL: | |
| Notes: | Article -- Export Date: 12 December 2016 -- Source: Scopus |
