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Cystathionine β-synthase (CBS) domains 1 and 2 fulfill different roles in ionic strength sensing of the ATP-binding cassette (ABC) transporter OpuA

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  • Akira Karasawa
  • ,
  • Guus B Erkens
  • ,
  • Ronnie P-A Berntsson
  • ,
  • Renee Otten
  • ,
  • Gea K Schuurman-Wolters
  • ,
  • Frans A.A. Mulder
  • Bert Poolman
The cystathionine β-synthase module of OpuA in conjunction with an anionic membrane surface acts as a sensor of internal ionic strength, which allows the protein to respond to osmotic stress. We now show by chemical modification and cross-linking studies that CBS2-CBS2 interface residues are critical for transport activity and/or ionic regulation of transport, whereas CBS1 serves no functional role. We establish that Cys residues in CBS1, CBS2, and the nucleotide-binding domain are more accessible for cross-linking at high than low ionic strength, indicating that these domains undergo conformational changes when transiting between the active and inactive state. Structural analyses suggest that the cystathionine β-synthase module is largely unstructured. Moreover, we could substitute CBS1 by a linker and preserve ionic regulation of transport. These data suggest that CBS1 serves as a linker and the structured CBS2-CBS2 interface forms a hinge point for ionic strength-dependent rearrangements that are transmitted to the nucleotide-binding domain and thereby affect translocation activity.
Original languageEnglish
JournalJournal of Biological Chemistry
Pages (from-to)37280-91
Number of pages12
Publication statusPublished - 2011

    Research areas

  • ATP-Binding Cassette Transporters, Adenosine Triphosphatases, Bacterial Proteins, Biological Transport, Cystathionine beta-Synthase, Escherichia coli, Lactococcus lactis, Osmolar Concentration, Protein Structure, Tertiary

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