Disorder-order folding transitions underlie catalysis in the helicase motor of SecA

Dimitra Keramisanou, Nikolaos Biris, Ioannis Gelis, Georgios Sianidis, Spyridoula Karamanou, Anastassios Economou, Charalampos G. Kalodimos

Research output: Contribution to journalArticlepeer-review

67 Scopus citations


SecA is a helicase-like motor that couples ATP hydrolysis with the translocation of extracytoplasmic protein substrates. As in most helicases, this process is thought to occur through nucleotide-regulated rigid-body movement of the motor domains. NMR, thermodynamic and biochemical data show that SecA uses a novel mechanism wherein conserved regions lining the nucleotide cleft undergo cycles of disorder-order transitions while switching among functional catalytic states. The transitions are regulated by interdomain interactions mediated by crucial 'arginine finger' residues located on helicase motifs. Furthermore, we show that the nucleotide cleft allosterically communicates with the preprotein substrate-binding domain and the regulatory, membrane-inserting C domain, thereby allowing for the coupling of the ATPase cycle to the translocation activity. The intrinsic plasticity and functional disorder-order folding transitions coupled to ligand binding seem to provide a precise control of the catalytic activation process and simple regulation of allosteric mechanisms.

Original languageEnglish (US)
Pages (from-to)594-602
Number of pages9
JournalNature Structural and Molecular Biology
Issue number7
StatePublished - Jul 2006
Externally publishedYes

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology


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