Distinct subunit architecture and assembly pattern of DNA gyrase from mycobacteria

• Published in: Molecular microbiology 2023-06, Vol.119 (6), p.728-738
• Main Authors: Faheem, Iqball, Gupta, Richa, Nagaraja, Valakunja
• Format: Article
• Language: English
• Subjects: Assembly; Binding; Coliforms; Deoxyribonucleic acid; DNA; DNA gyrase; DNA supercoiling; DNA topoisomerase; E coli; Escherichia coli; gyrase A; gyrase B; mycobacteria; Mycobacterium smegmatis; Mycobacterium tuberculosis; Supercoiling; Tuberculosis
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/mmi.15068

DNA gyrase, the sole negative supercoiling type II topoisomerase, is composed of two subunits, GyrA and GyrB, encoded by the gyrA and gyrB genes, respectively, that form a quaternary complex of A2B2. In this study, we have investigated the assembly of mycobacterial DNA gyrase from its individual subunits, a step prerequisite for its activity. Using analytical size‐exclusion chromatography, we show that GyrA from Mycobacterium tuberculosis and Mycobacterium smegmatis forms tetramers (A4) in solution unlike in Escherichia coli and other bacteria where GyrA exists as a dimer. GyrB, however, persists as a monomer, resembling the pattern found in E. coli. GyrB in both mycobacterial species interacts with GyrA and triggers the dissociation of the GyrA tetramer to facilitate the formation of catalytically active A2B2. Despite oligomerisation, the GyrA tetramer retained its DNA binding ability, and DNA binding had no effect on GyrA's oligomeric state in both species. Moreover, the presence of DNA facilitated the assembly of holoenzyme in the case of M. smegmatis by stabilising the GyrA2B2 tetramer but with little effect in M. tuberculosis. Thus, in addition to the distinct organisation and regulation of the gyr locus in mycobacteria, the enzyme assembly also follows a different pattern. Upon translation of dicistronic gyrB‐gyrA mRNA, GyrB remains monomer and GyrA forms tetramer. Monomeric GyrB binds GyrA tetramer to form A2B2 functional enzyme complex.