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SecA: a tale of two protomers

Marios Frantzeskos Sardis, Anastassios Economou · Molecular Microbiology · 2010

SummaryBacteria, Archaea and Eukaryotes have evolved a plethora of mechanisms to translocate proteins across their various membranes. The bacterial Sec pathway is ubiquitous and essential for cell viability and is used by most proteins destined for the inner membrane, the periplasm or beyond. In bacteria, Sec system components include the heterotrimers SecY/SecE/SecG and SecD/SecF/YajC and the peripherally associated ATPase motor SecA. SecA in solution is mainly dimeric. Unexpectedly, structures of SecA dimers from different or even the same bacterium do not have a consistent dimerization interface. Analysis of the functional assembled translocase complexes blurs the picture even further as the functional quaternary state of the SecYEG channel is also disputed. Several experimental approaches tried to define the oligomeric state of SecA during preprotein ‘pushing’ through SecYEG. One high‐resolution SecA–SecYEG complex has been visualized. This snapshot might be a step closer to the actual translocating machinery. Nevertheless, because of the use of detergent, the true quartenary state of the translocase might have been disturbed. Hence, even after this and other studies, several i

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