Protein mobility in the cytoplasm of Escherichia coli

Michael B. Elowitz, Michael G. Surette, Pierre Etienne Wolf, Jeffry B. Stock, Stanislas Leibler

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442 Scopus citations

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, D(a), of GFP in E. coli DH5α was found to be 7.7 ± 2.5 μm2/s. A 72-kDa fusion protein composed of GFP and a cytoplasmically localized maltose binding protein domain moves more slowly, with D(a), of 2.5 ± 0.6 μm2/s. In addition, GFP mobility can depend strongly on at least two factors: first, D(a) is reduced to 3.6 ± 0.7 μm2/s at high levels of GFP expression; second, the addition to GFP of a small tag consisting of six histidine residues reduces D(a) to 4.0 ± 2.0 μm2/s. Thus, a single effective cytoplasmic viscosity cannot explain all values of D(a) reported here. These measurements have implications for the understanding of intracellular biochemical networks.

Original languageEnglish (US)
Pages (from-to)197-203
Number of pages7
JournalJournal of bacteriology
Volume181
Issue number1
DOIs
StatePublished - Jan 1999

All Science Journal Classification (ASJC) codes

  • Microbiology
  • Molecular Biology

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