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Open and shut: Crystal structures of the dodecylmaltoside solubilized mechanosensitive channel of small conductance from Escherichia coli and Helicobacter pylori at 4.4 Å and 4.1 Å resolutions

Authors

  • Jeffrey Y. Lai,

    1. Division of Chemistry and Chemical Engineering, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, California 91125
    Current affiliation:
    1. Sapphire Energy, La Jolla, California
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    • Jeffrey Y. Lai and Yan Shuen Poon contributed equally to this work.

  • Yan Shuen Poon,

    1. Division of Chemistry and Chemical Engineering, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, California 91125
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    • Jeffrey Y. Lai and Yan Shuen Poon contributed equally to this work.

  • Jens T. Kaiser,

    1. Division of Chemistry and Chemical Engineering, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, California 91125
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  • Douglas C. Rees

    Corresponding author
    1. Division of Chemistry and Chemical Engineering, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, California 91125
    • Division of Chemistry and Chemical Engineering 114-96, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125
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Abstract

The mechanosensitive channel of small conductance (MscS) contributes to the survival of bacteria during osmotic downshock by transiently opening large diameter pores for the efflux of cellular contents before the membrane ruptures. Two crystal structures of the Escherichia coli MscS are currently available, the wild type protein in a nonconducting state at 3.7 Å resolution (Bass et al., Science 2002; 298:1582–1587) and the Ala106Val variant in an open state at 3.45 Å resolution (Wang et al., Science 2008; 321:1179–1183). Both structures used protein solubilized in the detergent fos-choline-14. We report here crystal structures of MscS from E. coli and Helicobacter pylori solubilized in the detergent β-dodecylmaltoside at resolutions of 4.4 and 4.2 Å, respectively. While the cytoplasmic domains are unchanged in these structures, distinct conformations of the transmembrane domains are observed. Intriguingly, β-dodecylmaltoside solubilized wild type E. coli MscS adopts the open state structure of A106V E. coli MscS, while H. pylori MscS resembles the nonconducting state structure observed for fos-choline-14 solubilized E. coli MscS. These results highlight the sensitivity of membrane protein conformational equilibria to variations in detergent, crystallization conditions, and protein sequence.

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