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The incisions in the DNA at the 3′- and 5′-side of a DNA damage during nucleotide excision repair in Escherichia coli occur in a complex consisting of damaged DNA, UvrB and UvrC. The exact requirements for the two incision events, however, are different. It has previously been shown that the 3′-incision requires the interaction between the C-terminal domain of UvrB and a homologous region in UvrC. This interaction, however, is dispensable for the 5′-incision. Here we show that the C-terminal domain of the UvrC protein is essential for the 5′-incision, whereas this domain can be deleted without affecting the 3′-incision. The C-terminal domain of UvrC is homologous with the C-terminal part of the ERCC1 protein which, in a complex with XPF, is responsible for the 5′-incision reaction in human nucleotide excision repair. Both in the UvrC and the ERCC1 domain a Helix-hairpin-Helix (HhH) motif can …