title: Two copies of the SecY channel and acidic lipids are necessary to activate the SecA translocation ATPase.
abstract: The SecA ATPase associates with the SecY complex to push preproteins across the bacterial membrane. Because a single SecY is sufficient to create the conducting channel, the function of SecY oligomerization remains unclear. Here, we have analyzed the translocation reaction using nanodiscs. We show that one SecY copy is sufficient to bind SecA and the preprotein, but only the SecY dimer together with acidic lipids supports the activation of the SecA translocation ATPase. In discs, the dimer is predominantly arranged in a back-to-back manner and remains active even if a constituent SecY copy is defective for SecA binding. In membrane vesicles and in intact cells, the coproduction of two inactive SecYs, one for channel gating and the other for SecA binding, recreates a functional translocation unit. These results indisputably argue that the SecY dimer is crucial for the activation of SecA, which is necessary for preprotein transport.
authors.affiliation: Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada V6T 1Z3.
authors.forename: Kush
authors.initials: K
authors.lastname: Dalal
authors.forename: Catherine S
authors.initials: CS
authors.lastname: Chan
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Sligar
authors.forename: Franck
authors.initials: F
authors.lastname: Duong
mesh_terms: D000143:Acids / Q000737:chemistry; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D004789:Enzyme Activation; D005816:Genetic Complementation Test; D008055:Lipids / Q000737:chemistry*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D050505:Mutant Proteins / Q000378:metabolism; D049329:Nanostructures / Q000737:chemistry; D011485:Protein Binding; D055503:Protein Multimerization; D021382:Protein Sorting Signals; D021381:Protein Transport; D000069816:SEC Translocation Channels; D000081416:SecA Proteins
chemical_list: D000143:Acids; D001426:Bacterial Proteins; D008055:Lipids; D026901:Membrane Transport Proteins; D050505:Mutant Proteins; D021382:Protein Sorting Signals; D000069816:SEC Translocation Channels; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins