The maltose ATP-binding cassette transporter in the 21st century – towards a structural dynamic perspective on its mode of action

Authors

  • Enrica Bordignon,

    Corresponding author
    1. ETH Zurich, Laboratory of Physical Chemistry, Wolfgang-Pauli-Str. 10. CH-8093 Zurich, Switzerland
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  • Mathias Grote,

    1. Humboldt University of Berlin, Department of Biology, Division of Microbial Physiology, Chausseestr. 117, D-10115 Berlin, Germany
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    • Present address: ESRC Research Centre for Genomics in Society (Egenis), University of Exeter, Byrne House, St. German's Road, Exeter EX4 4PJ, UK.

  • Erwin Schneider

    Corresponding author
    1. Humboldt University of Berlin, Department of Biology, Division of Microbial Physiology, Chausseestr. 117, D-10115 Berlin, Germany
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  • This article is dedicated to Professor Dr Winfried Boos (University of Konstanz) in recognition of his contributions to the current knowledge on the maltose system.

E-mail enrica.bordignon@phys.chem.ethz.ch; Tel. (+41) 44 6337570; Fax (+41) 44 6331448;

E-mail erwin.schneider@rz.hu-berlin.de; Tel. (+49) 30 20938121; Fax (+49) 30 20938126.

Summary

The maltose/maltodextrin transport system of Escherichia coli/Salmonella, composed of periplasmic maltose-binding protein, MalE, the pore-forming subunits MalF and MalG, and a homodimer of the nucleotide-binding subunit, MalK, serves as a model for canonical ATP-binding cassette importers in general. The wealth of knowledge accumulated on the maltose transporter in more than three decades by genetic, molecular genetic and biochemical means was complemented more recently by crystal structures of the isolated MalK dimer and of two conformational states of the full transporter. Here, we summarize insights into the transport mechanism provided by these structures and draw the reader's attention to experimental tools by which the dynamics of the transporter can be studied during substrate translocation. A transport model is presented that integrates currently available biochemical, biophysical and structural data. We also present the state of knowledge on regulatory functions of the maltose transporter associated with the C-terminal domain of MalK. Finally, we will address the application of coarse-grained modelling to visualize the progression of the conformational changes of an ABC transporter with special emphasis on the maltose system, which can provide a model platform for testing and validating the bioinformatic tools.

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