Dr Dmitry Ghilarov - John Innes Centre

Freeze-motion: mechanism of an ATP-powered supercoiling motor and its inhibition by new types of antibiotics revealed by cryoEM

Bacterial gyrase is essential for replication and transcription, and as such is a target of multiple antibiotics including fluoroquinolones. Gyrase is a molecular machine which channels the energy of ATP hydrolysis into negative supercoiling of DNA by stabilising and inverting a chiral DNA loop. Despite decades of study, the mechanistic basis for loop trapping is poorly understood & remains hypothetical. We have recently determined high-resolution cryoEM structures of the Escherichia coli gyrase-DNA holocomplex in a native pre-catalytic state, as well as several structures with novel types of natural & synthetic antibacterials targeting gyrase. Nucleotide-free structures constrain intact figure-of-eight supercoiled DNA loops, stabilised by the DNA-binding pulleys and poised for strand passage. Following binding of ATP, the ATPase domains of the enzyme undergo a dramatic ATP-induced shift and rotation. Comparison of different structures shows the transitions involved in DNA movement through the enzyme.