Structural and Comparative Stability of a Truncated N‐Terminal Domain of DNA Gyrase A From Salmonella Typhi

DNA Gyrase, a Type II topoisomerase, introduces negative supercoiling in dsDNA through the cleavage and religation activity at the expense of ATP. DNA Gyrase forms a hetero‐tetrameric complex with two Gyrase A and Gyrase B subunits. These two subunits interact dynamically to physically transfer one DNA duplex through another by coupling ATP binding and hydrolysis with DNA binding, cleavage, and strand transport. The N‐terminal domain of Gyrase A (GyrA‐NTD) mediates the cleavage of the DNA strand and forms the target site for quinolones class of antibiotics. While structures of GyrA‐NTD from several prokaryotes have been determined, the N‐terminal segment (residues 1–32) remains unresolved in apo forms. Here, we present the crystal structure of a truncated GyrA‐NTD (ΔGyrA‐NTD; residues 33–530) from Salmonella Typhi at 2.43 Å resolution, alongside comparative biophysical characterization with the wild type. Thermal and chemical denaturation assays revealed that the wild‐type GyrA‐NTD is more prone to unfolding than the truncated variant, indicating that deletion of the unresolved N‐terminal segment enhances domain stability. These findings uncover a structural element influencing GyrA‐NTD stability.