gyrB Protein, E.coli (Y5S, N198D)

gyrB protein, as a component of DNA gyrase, functions in the ATP-dependent negative supercoiling of closed circular double-stranded DNA, maintaining chromosomes in an underwound state. This activity enhances substrates for topoisomerase 4 (ParC and ParE), the principal enzyme responsible for unlinking newly replicated chromosomes in E. coli. gyrB catalyzes the interconversion of various topological isomers of double-stranded DNA rings, including the formation of catenanes. Additionally, it relaxes negatively supercoiled DNA in an ATP-independent manner. Notably, E. coli gyrase exhibits higher supercoiling activity compared to other characterized bacterial gyrases, introducing more supercoils faster than Mycobacterium tuberculosis gyrase. On the other hand, M. tuberculosis gyrase demonstrates higher decatenation activity than supercoiling in comparison to E. coli. Intriguingly, despite 777/804 identical residues, the GyrB subunit of S. typhimurium is toxic in E. coli, whereas the E. coli copy can be expressed in S. typhimurium. The enzymatic distinctions between E. coli gyrase and topoisomerase IV primarily stem from the GyrA C-terminal domain, particularly the GyrA-box. These insights emphasize the multifaceted role of gyrB in DNA topology regulation and its contribution to the functional diversity of gyrase enzymes across bacterial species.