eLife (Nov 2018)

CryoEM structures of open dimers of gyrase A in complex with DNA illuminate mechanism of strand passage

  • Katarzyna M Soczek,
  • Tim Grant,
  • Peter B Rosenthal,
  • Alfonso Mondragón

DOI
https://doi.org/10.7554/eLife.41215
Journal volume & issue
Vol. 7

Abstract

Read online

Gyrase is a unique type IIA topoisomerase that uses ATP hydrolysis to maintain the negatively supercoiled state of bacterial DNA. In order to perform its function, gyrase undergoes a sequence of conformational changes that consist of concerted gate openings, DNA cleavage, and DNA strand passage events. Structures where the transported DNA molecule (T-segment) is trapped by the A subunit have not been observed. Here we present the cryoEM structures of two oligomeric complexes of open gyrase A dimers and DNA. The protein subunits in these complexes were solved to 4 Å and 5.2 Å resolution. One of the complexes traps a linear DNA molecule, a putative T-segment, which interacts with the open gyrase A dimers in two states, representing steps either prior to or after passage through the DNA-gate. The structures locate the T-segment in important intermediate conformations of the catalytic cycle and provide insights into gyrase-DNA interactions and mechanism.

Keywords