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DNA gyrase subunit B

DNA gyrase negatively supercoils closed circular double-stranded DNA in an ATP-dependent manner to maintain chromosomes in an underwound state^{1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20}. This makes better substrates for topoisomerase 4 (ParC and ParE) which is the main enzyme that unlinks newly replicated chromosomes in E.coli²¹. Gyrase catalyzes the interconversion of other topological isomers of double-stranded DNA rings, including catenanes²². Relaxes negatively supercoiled DNA in an ATP-independent manner²³. E.coli gyrase has higher supercoiling activity than other characterized bacterial gyrases; at comparable concentrations E.coli gyrase introduces more supercoils faster than M.tuberculosis gyrase, while M.tuberculosis gyrase has higher decatenation than supercoiling activity compared to E.coli²⁴. E.coli makes 15% more negative supercoils in pBR322 plasmid DNA than S.typhimurium; the S.typhimurium GyrB subunit is toxic in E.coli, while the E.coli copy can be expressed in S.typhimurium even though the 2 subunits have 777/804 residues identical²⁵. The enzymatic differences between E.coli gyrase and topoisomerase IV are largely due to the GyrA C-terminal domain (approximately residues 524-841) and specifically the GyrA-box^26,27.

AlphaFold DB , UniProt , Accession P0AES6, Species ECOLI (Escherichia coli (strain K12)), Gene gyrB, Length 804 aa.