Single molecule studies of receptor proteins of Escherichia coli
Abstract
Protein organization inside live cells is essential to their life processes. The location of each protein is dynamic according to the interactions with their environment so that their time dependent mobility can provide unique information about their function. Single molecule imaging of live cells provides individual trajectories of molecules with high spatiotemporal resolution, 30 nm and up to 1000 frames per second, that can not be accessed by ensemble experiments. Coupled with a genetically well-controlled expression system and fluorescent protein fusion hybrids, application of Single Molecule Tracking after Photobleaching (SMTAP) techniques visualizes and tracks individual newly synthesized cytoplasmic membrane proteins in live E. coli. Polar localization mechanisms of the chemotaxis protein, Tsr, and the distribution and mobility of the translocon protein, TatB were investigated. Their motions in the cytoplasmic membrane of live Eschirichia coli show a deviation from Brownian motion with diffusion coefficient ranging 0.01–4.5 μm2s−1 according to time scales and reveal a complex membrane structure in Escherichia coli with inner barrier of 100–150 nm and outer barrier of 200–300 nm in diameter. This thesis also deals with the fluorescence on/off blinking mechanism in single GFP-like fluorescent proteins. A universal power law behavior of the on/off time duration of Venus FP was observed in both on glass and in cytoplasm of E. coli cell.
Degree
Ph.D.
Advisors
Ritchie, Purdue University.
Subject Area
Cellular biology|Microbiology|Biophysics
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