| Autor: |
Seinen AB; Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, and the Zernike Institute for Advanced Materials, University of Groningen, Groningen, The Netherlands.; AMOLF, Science Park 104, 1098 XG, Amsterdam, The Netherlands., Spakman D; Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, and the Zernike Institute for Advanced Materials, University of Groningen, Groningen, The Netherlands., van Oijen AM; School of Chemistry, University of Wollongong, Wollongong, Australia., Driessen AJM; Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, and the Zernike Institute for Advanced Materials, University of Groningen, Groningen, The Netherlands. a.j.m.driessen@rug.nl. |
| Abstrakt: |
In bacteria, the SecA ATPase provides the driving force for protein secretion via the SecYEG translocon. While the dynamic interplay between SecA and SecYEG in translocation is widely appreciated, it is not clear how SecA associates with the translocon in the crowded cellular environment. We use super-resolution microscopy to directly visualize the dynamics of SecA in Escherichia coli at the single-molecule level. We find that SecA is predominantly associated with and evenly distributed along the cytoplasmic membrane as a homodimer, with only a minor cytosolic fraction. SecA moves along the cell membrane as three distinct but interconvertible diffusional populations: (1) A state loosely associated with the membrane, (2) an integral membrane form, and (3) a temporarily immobile form. Disruption of the proton-motive-force, which is essential for protein secretion, re-localizes a significant portion of SecA to the cytoplasm and results in the transient location of SecA at specific locations at the membrane. The data support a model in which SecA diffuses along the membrane surface to gain access to the SecYEG translocon. |
