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Protein Mobility in the Cytoplasm of Escherichia coli

Elowitz, Michael B. and Surette, Michael G. and Wolf, Pierre-Etienne and Stock, Jeffrey B. and Leibler, Stanislas (1999) Protein Mobility in the Cytoplasm of Escherichia coli. Journal of Bacteriology, 181 (1). pp. 197-203. ISSN 0021-9193. http://resolver.caltech.edu/CaltechAUTHORS:ELOjbact99

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Abstract

The rate of protein diffusion in bacterial cytoplasm may constrain a variety of cellular functions and limit the rates of many biochemical reactions in vivo. In this paper, we report noninvasive measurements of the apparent diffusion coefficient of green fluorescent protein (GFP) in the cytoplasm of Escherichia coli. These measurements were made in two ways: by photobleaching of GFP fluorescence and by photoactivation of a red-emitting fluorescent state of GFP (M. B. Elowitz, M. G. Surette, P. E. Wolf, J. Stock, and S. Leibler, Curr. Biol. 7:809-812, 1997). The apparent diffusion coefficient, Da, of GFP in E. coli DH5alpha was found to be 7.7 ± 2.5 µm^2/s. A 72-kDa fusion protein composed of GFP and a cytoplasmically localized maltose binding protein domain moves more slowly, with Da of 2.5 ± 0.6 µm^2/s. In addition, GFP mobility can depend strongly on at least two factors: first, Da is reduced to 3.6 ± 0.7 µm^2/s at high levels of GFP expression; second, the addition to GFP of a small tag consisting of six histidine residues reduces Da to 4.0 ± 2.0 µm^2/s. Thus, a single effective cytoplasmic viscosity cannot explain all values of Da reported here. These measurements have implications for the understanding of intracellular biochemical networks.


Item Type:Article
Additional Information:Copyright © 1999, American Society for Microbiology. Received 7 August 1998/Accepted 21 October 1998. We thank B. Aguera y Arcas, U. Alon, T. Holy, and A. C. Maggs for help with data analysis and software. We also thank U. Alon, P. Cluzel, L. Frisen, P. Lopez, and T. Surrey for critical reading of the manuscript. We are grateful to B. P. Cormack for providing GFP mutants.
Record Number:CaltechAUTHORS:ELOjbact99
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:ELOjbact99
Alternative URL:http://jb.asm.org/cgi/content/abstract/181/1/197
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ID Code:7094
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Deposited On:08 Jan 2007
Last Modified:26 Dec 2012 09:28

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