Investigating Intracellular Dynamics of FtsZ Cytoskeleton with Photo-activation Single-molecule Tracking

¹ UConn Health Center
² University of Connecticut Health Center

^* To whom correspondence should be addressed. E-mail: jyu{at}uchc.edu.

Submitted on February 7, 2008
Revised on March 3, 2008
Accepted on 27 March 2008

	Abstract

Using photo-activatable fluorescent protein (PAFP) as an intracellular protein label for single-molecule tracking offers several advantages over the traditional methods. Here we demonstrate the technique of photo-activation single-molecule tracking by investigating the mobility dynamics of intracellular FtsZ protein molecules in live Escherichia coli cells. FtsZ is a prokaryotic cytoskeleton protein (a homologue of tubulin) and plays important roles in cytokinesis. We demonstrate two heterogeneous sub-populations of FtsZ molecules with distinct diffusional dynamics. The FtsZ molecules forming the Z-rings near the center of the cell were mostly stationary, consistent with the assumption that they are within polymeric filamentous structures. The rest of the FtsZ molecules, on the other hand, undergo Brownian motion spanning the whole cell length. Surprisingly, the diffusion of FtsZ is spatially restricted to helical-shaped regions, implying an energy barrier for free diffusion. Consistently, the measured mean square displacements of FtsZ showed anomalous diffusion characteristics. These results demonstrated the feasibility and advantages of photo-activation single-molecule tracking, and suggested new levels of complexity in the prokaryotic membrane organization.

Key Words: bacterial cytoskeleton, photo-activatable fluorescent protein, single-molecule tracking