Nucleic Acids Research, 2002, Vol. 30, No. 11 2492-2500
© 2002 Oxford University Press
The C-terminal region of Escherichia coli UvrC contributes to the flexibility of the UvrABC nucleotide excision repair system
Laboratory of Molecular Genetics and 1Laboratory of Bio-organic chemistry, Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, Einsteinweg 55, PO Box 9502, 2300 RA Leiden, The Netherlands
Nucleotide excision repair in Escherichia coli involves formation of the UvrBDNA complex and subsequent DNA incisions on either site of the damage by UvrC. In this paper, we studied the incision of substrates with different damages in varying sequence contexts. We show that there is not always a correlation between the incision efficiency and the stability of the UvrBDNA complex. Both stable and unstable UvrBDNA complexes can be efficiently incised. However some lesions that give rise to stable UvrBDNA complexes do result in a very low incision. We present evidence that this poor incision is due to sterical hindrance of the damage itself. In its C-terminal region UvrC contains two helixhairpinhelix (HhH) motifs. Mutational analysis shows that these motifs constitute one functional unit, probably folded as one structural unit; the (HhH)2 domain. This (HhH)2 domain was previously shown to be important for the 5' incision on a substrate containing a (cis-Pt)·GG adduct, but not for 3' incision. Here we show that, mainly depending on the sequence context of the lesion, the (HhH)2 domain can be important for 3' and/or 5' incision. We propose that the (HhH)2 domain stabilises specific DNA structures required for the two incisions, thereby contributing to the flexibility of the UvrABC repair system.
* To whom correspondence should be addressed. Tel: +31 71 5274773; Fax: +31 71 5274537; Email: n.goosen{at}chem.leidenuniv.nl
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