Structural Studies of E. coli DNA Gyrase Complexes: Molecular Recognition of DNA Topology and Conformational Regulation

Date

Sep 24, 2026

Time

3:00 PM - 4:00 PM

Speaker

Naveen Kumar Murugasamy

Affiliation

IGBMC, Strasbourg, France

Language

en

Main Topic

Biologie

Host

Alexander von Appen

Description

Maintaining negatively supercoiled (-SC) topological homeostasis in the bacterial chromosome is essential for genome stability, replication fidelity, and transcriptional regulation. As DNA and RNA polymerases track along the double helix, they generate mechanical stress, producing downstream positive supercoils (+SC) that can stall macromolecular machineries. In bacteria, the type II topoisomerase DNA gyrase uniquely relieves this topological strain through a tightly regulated homeostatic feedback loop, modulating gyrA and gyrB expression in response to DNA relaxation. While gyrase is known to be biochemically versatile, catalyzing ATP-dependent negative supercoiling, ATP-dependent positive supercoil relaxation, and ATP-independent negative supercoil relaxation, its catalytic efficacy depends entirely on its capacity to distinguish between these topological states. Despite extensive biochemical characterization, the structural basis governing how DNA gyrase senses DNA chirality and selectively engages supercoiled substrates has remained fundamentally unresolved. To address this question, this study presents high-resolution cryo-electron microscopy structures of DNA gyrase trapped in complex with (+) and (–) supercoiled minicircle DNA substrates. By capturing these distinct topological assemblies, the resulting reconstructions reveal the critical C-terminal domain (CTD) interactions and large-scale conformational transitions that mediate chirality discrimination and dictate the directionality of strand passage. Furthermore, this study reports the structural determination of a novel DNA-free conformation of DNA gyrase, a resting state intermediate hypothesized from kinetic experiments but never previously visualized at near-atomic resolution. Together, these findings define the conformational steps leading to supercoil chirality sensing, establishing a definitive mechanistic model for how DNA gyrase maintains topological integrity within the bacterial cell.

Last modified: Sep 10, 2026, 7:39:47 AM