Fig. 1: The importance of Ku for mycobacterial survival under DNA double-strand break conditions and cryo-EM of Apo-Ku-Mtb.

M. smegmatis strains from stationary phase were exposed to 0.1% (v/v) MMS (A) or subjected to desiccation for 24 h. B CFU counts were determined before and after treatments on 7H10 agar. Δku – ku deletion mutant, ΔkupMV306 - ku deletion mutant with empty plasmid; ΔkupMV306::kusm – complemented ku deletion mutant containing pMV::msmeg5580. Results of two independent experiments, done with three biological replicates. ns – non-significant, **** p < 0.0001, one way ANOVA or unpaired t test. C Representative 2D class averages of apo-Ku-Mtb. D Cryo-EM map and model for apo-Ku-Mtb. The map is shown as a transparent grey to 4.04 Å resolution. Protomer A is shown in pink and protomer B in blue, the C-terminal extensions are shown in darker colours. E) Domain organisation schematic for Ku-Mtb and human Ku70/80. Ku-Mtb is shown in pink and blue. Ku70 vWA is shown in yellow and the DNA binding domain in orange. Ku80 vWA is coloured in lime green and the DNA binding domain in dark green. F) A comparison of Ku-Mtb (This study) and human Ku70/80 (PDB:1JEY). The models are coloured according to E.