Helicases unwind duplex DNA and are required for a multitude of cellular activities. The majority of Superfamily one (SF1) helicases unwind duplex DNA with 3' - 5' directionality and have been studied in depth. However, there is a set of SF1 helicases with 5' - 3' directionality, the mechanism of which is yet to be understood. The initial research of this thesis was to determine the role of the 2B domain of the SF1 3' -5' helicase, Bacillus stearothermophilus PcrA using modified inteins. However, this work, and work attempting to use the same modified inteins to study the Replication Factor C dependent loading of Proliferating Cell Nuclear Antigen onto DNA, proved unsuccessful. The crystal structure of the E.coli RecBCD complex has been solved previously and gives some insights into the 5'- 3' helicase mechanism of the SF1 helicase RecD. Due to stability problems, isolated E.coli RecD protein is an unsuitable target for characterisation therefore RecD homologues from other species were examined. The RecD homologue from Deinococcus radiodurans (drRecD2) was found to be soluble and was chosen for biochemical and structural characterisation. Mutational studies were carried out to investigate the molecular mechanism by which drRecDl unwinds duplex DNA. A molecular pin has been identified and is implicated in splitting open duplex DNA as part of the helicase mechanism. In addition to biochemical characterisation, drRecD2 was crystallised with a 5'-tailed duplex DNA substrate. The crystalisation conditions were optimised leading to diffraction data of 3.5A resolution.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:498882 |
| Date | January 2008 |
| Creators | Griffiths, Stuart Peter |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://discovery.ucl.ac.uk/1443979/ |
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