Strand-specific loading of DnaB helicase by DnaA to a substrate mimicking unwound oriC |
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Authors: | Weigel Christoph Seitz Harald |
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Institution: | Max-Planck-Institut für molekulare Genetik, Berlin, Germany. |
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Abstract: | We analysed the enzymatic activity (strand dis-placement) of the Escherichia coli DnaB helicase on a mirror-image pair of oligonucleotide-based substrates mimicking the unwound replication origin oriC. Loading of the helicase complex occurred exclusively to the single-stranded 'lower strand' part of the substrates. Full helicase activity required DnaA bound to the double-stranded part of the substrates (oriC DnaA box R1) and to their single-stranded 'upper strand' part. We assume that in vivo DnaA also loads the first of two helicase complexes - required for the assembly of two replication forks - to the lower strand of oriC during initiation of bidirectional chromosome replication in E. coli. |
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