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9 February 2012 Diffusion properties of single FoF1-ATP synthases in a living bacterium unraveled by localization microscopy
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Abstract
FoF1-ATP synthases in Escherichia coli (E. coli) bacteria are membrane-bound enzymes which use an internal protondriven rotary double motor to catalyze the synthesis of adenosine triphosphate (ATP). According to the 'chemiosmotic hypothesis', a series of proton pumps generate the necessary pH difference plus an electric potential across the bacterial plasma membrane. These proton pumps are redox-coupled membrane enzymes which are possibly organized in supercomplexes, as shown for the related enzymes in the mitochondrial inner membrane. We report diffusion measurements of single fluorescent FoF1-ATP synthases in living E. coli by localization microscopy and single enzyme tracking to distinguish a monomeric enzyme from a supercomplex-associated form in the bacterial membrane. For quantitative mean square displacement (MSD) analysis, the limited size of the observation area in the membrane with a significant membrane curvature had to be considered. The E. coli cells had a diameter of about 500 nm and a length of about 2 to 3 μm. Because the surface coordinate system yielded different localization precision, we applied a sliding observation window approach to obtain the diffusion coefficient D = 0.072 μm2/s of FoF1-ATP synthase in living E. coli cells.
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Marc Renz, Torsten Rendler, and Michael Börsch "Diffusion properties of single FoF1-ATP synthases in a living bacterium unraveled by localization microscopy", Proc. SPIE 8225, Imaging, Manipulation, and Analysis of Biomolecules, Cells, and Tissues X, 822513 (9 February 2012); https://doi.org/10.1117/12.907089
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