A two-subunit type I DNA topoisomerase (reverse gyrase) from an extreme hyperthermophile
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Updated: Nov 6, 2026

Iterative Optimization of DNA Duplexes for Crystallization of SeqA-DNA Complexes
Published on: November 1, 2012
R Krah1, S A Kozyavkin, A I Slesarev
1Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Abstract:
A recently described reverse gyrase from the hyperthermophilic methanogen Methanopyrus kandleri is the only known example of a heterodimeric type I topoisomerase. The enzyme is made up of a 42-kDa subunit which covalently interacts with DNA (RgyA) and a 138-kDa subunit which binds ATP (RgyB). We have now cloned and sequenced the genes for both subunits of this enzyme. Surprisingly, the universally conserved type I topoisomerase domain [Lima, C. D., Wang, J. C. & Mondragon, A. (1994) Nature (London) 367, 138-146] which has been found as a contiguous polypeptide in the prokaryotes and eukaryotes is shared between the protomers. The subdomain with the active-site tyrosine is entirely within RgyA, whereas the subdomain implicated in noncovalent binding of the cleaved DNA strand is contained entirely in RgyB. The appearance of this unique structure in a highly conserved enzyme family supports the hypothesis that the methanogens branched from other prokaryotes and eukaryotes very early in evolution.
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