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Replication of the colicin E1 plasmid in extracts of Escherichia coli: Uncoupling of leading strand from lagging strand synthesis

✍ Scribed by Staudenbauer, Walter L. ;Scherzinger, Eberhard ;Lanka, Erich

Publisher: Springer
Year: 1979
Tongue: English
Weight: 722 KB
Volume: 177
Category: Article
ISSN: 0026-8925
DOI: 10.1007/bf00267260

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✦ Synopsis

The replication of the ColEl plasmid was studied in extracts from E. coli dnaG mutants. It was found that the synthesis of the complementary strands of ColEl DNA can be carried out in these extracts in two consecutive steps: (1) synthesis of the leading L strand independent of the dnaG function, and (2) synthesis of the lagging H strand depending upon addition of wild-type dnaG protein. In contrast to L strand synthesis, the latter reaction is insensitive to rifampicin and novobiocin. Both synthetic pathways are however blocked by antiserum directed against dnaB protein. This indicates an additional role of the dnaB protein in duplex DNA replication besides assisting the dnaG protein in the priming of lagging strand synthesis. The T7 gene-4 protein acting in conjunction with T7 DNA polymerase can substitute for both the function of the dnaB and dnaG protein. It is concluded that plasmid replication proceeds by a semi-discontinuous mechanism.

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An E. coli strain which carries a mutation conferring clorobiocin resistance and temperature sensitivity for growth has recently been described and evidence has been presented suggesting that the mutation is located in the gyrB gene (Orr et al. 1979). The replication of the ColE1 plasmid was analyse