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Updated: May 28, 2026

Characterization of Membrane Transporters by Heterologous Expression in E. coli and Production of Membrane Vesicles
Published on: December 31, 2019
Structure and function of the glucose PTS transporter from Escherichia coli
Jean-Marc Jeckelmann1, Daniel Harder, Stefania A Mari
1Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, CH-3012 Bern, Switzerland.
Abstract:
The glucose transporter IICB of the Escherichia coli phosphotransferase system (PTS) consists of a polytopic membrane domain (IIC) responsible for substrate transport and a hydrophilic C-terminal domain (IIB) responsible for substrate phosphorylation. We have overexpressed and purified a triple mutant of IIC (mut-IIC), which had recently been shown to be suitable for crystallization purposes. Mut-IIC was homodimeric as determined by blue native-PAGE and gel-filtration, and had an eyeglasses-like structure as shown by negative-stain transmission electron microscopy (TEM) and single particle analysis. Glucose binding and transport by mut-IIC, mut-IICB and wildtype-IICB were compared with scintillation proximity and in vivo transport assays. Binding was reduced and transport was impaired by the triple mutation. The scintillation proximity assay allowed determination of substrate binding, affinity and specificity of wildtype-IICB by a direct method. 2D crystallization of mut-IIC yielded highly-ordered tubular crystals and made possible the calculation of a projection structure at 12Å resolution by negative-stain TEM. Immunogold labeling TEM revealed the sidedness of the tubular crystals, and high-resolution atomic force microscopy the surface structure of mut-IIC. This work presents the structure of a glucose PTS transporter at the highest resolution achieved so far and sets the basis for future structural studies.
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Glucose Transporters
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Secondary Active Transport
Secondary Active Transport
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