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Bacterial preprotein translocase: mechanism and conformational dynamics of a processive enzyme
Author(s) -
Economou Anastassios
Publication year - 1998
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1998.00713.x
Subject(s) - translocase , biology , atp hydrolysis , protein subunit , lipid bilayer , membrane transport protein , biochemistry , aaa proteins , biophysics , atpase , translocase of the inner membrane , translocase of the outer membrane , inner membrane , microbiology and biotechnology , membrane protein , membrane , enzyme , protein targeting , mitochondrial membrane transport protein , gene , chromosomal translocation
Preprotein translocase, the membrane transporter for secretory proteins, is a processive enzyme. It comprises the membrane proteins SecYEG(DFYajC) and the peripheral ATPase SecA, which acts as a motor subunit. Translocase subunits form dynamic complexes in the lipid bilayer and build an aqueous conduit through which preprotein substrates are transported at the expense of energy. Preproteins bind to translocase and trigger cycles of ATP binding and hydrolysis that drive a transition of SecA between two distinct conformational states. These changes are transmitted to SecG and lead to inversion of its membrane topology. SecA conformational changes promote directed migration of the polymeric substrate through the translocase, in steps of 20–30 aminoacyl residues. Translocase dissociates from the substrate only after the whole preprotein chain length has been transported to the trans side of the membrane, where it is fully released.