Molecular basis of UV-sensitive mutant strain MBH3 of Haemophilus influenzae Rd: identification of mutation in the...

We have previously reported on cloning a DNA repair gene designated as uvr3 by virtue of its ability to phenotypically complement the UV sensitivity of mutant strain MBH3. Subsequently, we identified the uvr3 gene to be the uvrA gene (gene identification number HI0249) of Haemophilus influenzae Rd. The uvrA gene is a component of the UvrABC excision repair pathway. We studied molecular basis of the UV sensitivity of the MBH3 strain and identified a G-->A transition at nucleotide position 2700 of the uvrA gene, altering the Trp-900 codon (TGG) to a nonsense codon (TGA). Thus, the UvrA protein produced in the mutant strain MBH3 is likely to be truncated and unable to carry out the UV-induced DNA repair, thereby rendering the strain UV sensitive.