Preprotein-controlled catalysis in the helicase motor of SecA.
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.
Karamanou
Spyridoula
S
Institute of Molecular Biology and Biotechnology, Foundation of Research and Technology-Hellas, Crete, Greece.
Gouridis
Giorgos
G
Papanikou
Efrosyni
E
Sianidis
Giorgos
G
Gelis
Ioannis
I
Keramisanou
Dimitra
D
Vrontou
Eleftheria
E
Kalodimos
Charalampos G
CG
Economou
Anastassios
A
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D002384:Catalysis; D004789:Enzyme Activation; D026901:Membrane Transport Proteins / Q000378:metabolism*; D017510:Protein Folding; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D013696:Temperature
D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D000069816:SEC Translocation Channels; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins