New clues to the function of world record bacterium

07-05-2009

The Guinness Book of Records has listed it as the world’s toughest bacterium. In a paper in the journal Structure, the MX team at the ESRF has unveiled the structure of one of four proteins that become active when the bacterium Deinococcus radiodurans presents damage from ultraviolet light.

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The so-called UvrA proteins are key actors in recognising lesions in DNA and repairing them. The other Uvrs have different roles. UvrB is, together with UvrA, responsible for damage recognition. After the lesion has been located, UvrA dissociates from the DNA, whilst UvrB forms a complex on the DNA damage sites. UvrC binds to the UvrB-DNA complex and incises the DNA lesion. UvrD extracts a fragment of 12 to 13 nucleotides containing the damaged DNA and finally the gap is filled by DNA polymerase and ligase, which will repair the DNA. Uvrs are not only found in Deinococcus Radiodurans, they are also present in many other bacteria.

The scientists wrote in the paper that despite previous studies on similar proteins, the architecture of UvrA is “largely unexpected”. They identified the different areas in the protein that bind to the DNA. They also compared the structure with the structure of another UvrA from a different bacterium and found out that the insertion domains of the two proteins have a role in the DNA binding and the damage recognition. The information on the two proteins allowed the researchers to design a model for how UvrA functions.

 

Reference:

Timmins J. et al, Structure, Volume 17, Issue 4, 547-558, 15 April 2009.

Top image: Joanna Timmins, from the MX group, looks at the structure of UVrA2 in the screen. Credits: C. Argoud.