Preprotein-controlled catalysis in the helicase motor of SecA

Spyridoula Karamanou, Giorgos Gouridis, Efrosyni Papanikou, Giorgos Sianidis, Ioannis Gelis, Dimitra Keramisanou, Eleftheria Vrontou, Charalampos G. Kalodimos, Anastassios Economou

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


The cornerstone of the functionality of almost all motor proteins is the regulation of their activity by binding interactions with their respective substrates. In most cases, the underlying mechanism of this regulation remains unknown. Here, we reveal a novel mechanism used by secretory preproteins to control the catalytic cycle of the helicase 'DEAD' motor of SecA, the preprotein translocase ATPase. The central feature of this mechanism is a highly conserved salt-bridge, Gate1, that controls the opening/closure of the nucleotide cleft. Gate1 regulates the propagation of binding signal generated at the Preprotein Binding Domain to the nucleotide cleft, thus allowing the physical coupling of preprotein binding and release to the ATPase cycle. This relay mechanism is at play only after SecA has been previously 'primed' by binding to SecYEG, the transmembrane protein-conducting channel. The Gate1-controlled relay mechanism is essential for protein translocase catalysis and may be common in helicase motors.

Original languageEnglish (US)
Pages (from-to)2904-2914
Number of pages11
JournalEMBO Journal
Issue number12
StatePublished - Jun 20 2007
Externally publishedYes


  • ATPase
  • DEAD motor
  • Helicase
  • Protein secretion


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