%A Amar Deep
%A Latika Singh
%A Japleen Kaur
%A Maheshwaran Velusamy
%A Pushpanjali Bhardwaj
%A Ramandeep Singh
%A Krishan Gopal Thakur
%O The copyright of this article belongs to Cell Press/Science Direct
%J Structure (London, England : 1993)
%T Structural insights into DarT toxin neutralization by cognate DarG antitoxin: ssDNA mimicry by DarG C-terminal domain keeps the DarT toxin inhibited

%X In the DarTG toxin-antitoxin system, the DarT toxin ADP-ribosylates single-stranded DNA (ssDNA), which stalls DNA replication and plays a crucial role in controlling bacterial growth and bacteriophage infection. This toxic activity is reversed by the N-terminal macrodomain of the cognate antitoxin DarG. DarG also binds DarT, but the role of these interactions in DarT neutralization is unknown. Here, we report that the C-terminal domain of DarG (DarG toxin-binding domain [DarGTBD]) interacts with DarT to form a 1:1 stoichiometric heterodimeric complex. We determined the 2.2 ? resolution crystal structure of the Mycobacterium tuberculosis DarT-DarGTBD complex. The comparative structural analysis reveals that DarGTBD interacts with DarT at the DarT/ssDNA interaction interface, thus sterically occluding substrate ssDNA binding and consequently inactivating toxin by direct protein-protein interactions. Our data support a unique two-layered DarT toxin neutralization mechanism of DarG, which is important in keeping the toxin molecules in check under normal growth conditions.


%N 7
%K DNA mimic; DNA modification; DNA ribosylation; DarTG; Mycobacterium tuberculosis; toxin-antitoxin system; toxin-binding domain
%P 780-789
%V 31
%D 2023
%I Cell Press/Science Direct
%R 10.1016/j.str.2023.04.008
%L open3174