UvrA and UvrC subunits of the Mycobacterium tuberculosis UvrABC excinuclease interact independently of UvrB and DNA.

The UvrABC excinuclease plays a vital role in bacterial nucleotide excision repair. While UvrA and UvrB subunits associate to form a UvrA2 B2 complex, interaction between UvrA and UvrC has not been demonstrated or quantified in any bacterial species. Here, using Mycobacterium tuberculosis UvrA (MtUvrA), UvrB (MtUvrB) and UvrC (MtUvrC) subunits, we show that MtUvrA binds to MtUvrB and equally well to MtUvrC with submicromolar affinity. Furthermore, MtUvrA forms a complex with MtUvrC both in vivo and in vitro, independently of DNA and UvrB. Collectively, these findings reveal new insights into the pairwise relationships between the subunits of the UvrABC incision complex.