TY - JOUR TI - Structural basis for the inhibition of RecBCD by Gam and its synergistic antibacterial effect with quinolones AU - Wilkinson, Martin AU - Troman, Luca A AU - Wan Nur Ismah, Wan AK AU - Chaban, Yuriy AU - Avison, Matthew B AU - Dillingham, Mark S AU - Wigley, Dale B A2 - Sherratt, David VL - 5 PY - 2016 DA - 2016/12/23 SP - e22963 C1 - eLife 2016;5:e22963 DO - 10.7554/eLife.22963 UR - https://doi.org/10.7554/eLife.22963 AB - Our previous paper (Wilkinson et al, 2016) used high-resolution cryo-electron microscopy to solve the structure of the Escherichia coli RecBCD complex, which acts in both the repair of double-stranded DNA breaks and the degradation of bacteriophage DNA. To counteract the latter activity, bacteriophage λ encodes a small protein inhibitor called Gam that binds to RecBCD and inactivates the complex. Here, we show that Gam inhibits RecBCD by competing at the DNA-binding site. The interaction surface is extensive and involves molecular mimicry of the DNA substrate. We also show that expression of Gam in E. coli or Klebsiella pneumoniae increases sensitivity to fluoroquinolones; antibacterials that kill cells by inhibiting topoisomerases and inducing double-stranded DNA breaks. Furthermore, fluoroquinolone-resistance in K. pneumoniae clinical isolates is reversed by expression of Gam. Together, our data explain the synthetic lethality observed between topoisomerase-induced DNA breaks and the RecBCD gene products, suggesting a new co-antibacterial strategy. KW - DNA repair KW - RecBCD KW - antibacterials JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -