DNA gyrases catalyze negative supercoiling of DNA, are
essential
for bacterial DNA replication, transcription, and recombination, and
are important antibacterial targets in multiple pathogens, including Mycobacterium tuberculosis, which in 2021 caused
>1.5 million deaths worldwide. DNA gyrase is a tetrameric (A2B2) protein formed from two subunit types: gyrase
A (GyrA)
carries the breakage-reunion active site, whereas gyrase B (GyrB)
catalyzes ATP hydrolysis required for energy transduction and DNA
translocation. The GyrB ATPase domains dimerize in the presence of
ATP to trap the translocated DNA (T-DNA) segment as a first step in
strand passage, for which hydrolysis of one of the two ATPs and release
of the resulting inorganic phosphate is rate-limiting. Here, dynamical-nonequilibrium
molecular dynamics (D-NEMD) simulations of the dimeric 43 kDa N-terminal
fragment of M. tuberculosis GyrB show
how events at the ATPase site (dissociation/hydrolysis of bound nucleotides)
are propagated through communication pathways to other functionally
important regions of the GyrB ATPase domain. Specifically, our simulations
identify two distinct pathways that respectively connect the GyrB
ATPase site to the corynebacteria-specific C-loop, thought to interact
with GyrA prior to DNA capture, and to the C-terminus of the GyrB
transduction domain, which in turn contacts the C-terminal GyrB topoisomerase-primase
(TOPRIM) domain responsible for interactions with GyrA and the centrally
bound G-segment DNA. The connection between the ATPase site and the
C-loop of dimeric GyrB is consistent with the unusual properties of M. tuberculosis DNA gyrase relative to those from
other bacterial species.