Reverse gyrase: a helicase-like domain and a type I topoisomerase in the same polypeptide.
Reverse gyrase is a type I DNA topoisomerase able to positively supercoil DNA and is found in thermophilic archaebacteria and eubacteria. The gene coding for this protein was cloned from Sulfolobus acidocaldarius DSM 639. Analysis of the 1247-amino acid sequence and comparison of it with available sequence data suggest that reverse gyrase is constituted of two distinct domains: (i) a C-terminal domain of approximately 630 amino acids clearly related to eubacterial topoisomerase I (Escherichia coli topA and topB gene products) and to Saccharomyces cerevisiae top3; (ii) an N-terminal domain without any similarity to other known topoisomerases but containing several helicase motifs, including an ATP-binding site. These results are consistent with those from our previous mechanistic studies of reverse gyrase and suggest a model in which positive supercoiling is driven by the concerted action of helicase and topoisomerase in the same polypeptide: this constitutes an example of a composite gene formed by a helicase domain and a topoisomerase domain.
Confalonieri
F
F
Laboratoire d'Enzymologie des Acides Nucléiques, Université Paris Sud, Orsay, France.
Elie
C
C
Nadal
M
M
de La Tour
C
C
Forterre
P
P
Duguet
M
M
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics; D003001:Cloning, Molecular; D004264:DNA Topoisomerases, Type I / Q000235:genetics*; D004250:DNA Topoisomerases, Type II / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D039601:Eukaryotic Initiation Factor-4A; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D010448:Peptide Initiation Factors / Q000235:genetics; D015183:Restriction Mapping; D016415:Sequence Alignment; D016944:Sulfolobus / Q000201:enzymology / Q000235:genetics*
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D010448:Peptide Initiation Factors; D039601:Eukaryotic Initiation Factor-4A; D004264:DNA Topoisomerases, Type I; D004250:DNA Topoisomerases, Type II