title: Cystathionine β-synthase (CBS) domains 1 and 2 fulfill different roles in ionic strength sensing of the ATP-binding cassette (ABC) transporter OpuA.
abstract: 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.
authors: Department of Biochemistry, Groningen Biomolecular Science and Biotechnology Institute, Netherlands Proteomics Centre and Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands.
authors: Akira
authors: A
authors: Karasawa
authors: Guus B
authors: GB
authors: Erkens
authors: Ronnie P-A
authors: RP
authors: Berntsson
authors: Renee
authors: R
authors: Otten
authors: Gea K
authors: GK
authors: Schuurman-Wolters
authors: Frans A A
authors: FA
authors: Mulder
authors: Bert
authors: B
authors: Poolman
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D003541:Cystathionine beta-Synthase; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D013294:Lactococcus lactis / Q000201:enzymology* / Q000235:genetics; D009994:Osmolar Concentration; D017434:Protein Structure, Tertiary
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D000251:Adenosine Triphosphatases; D003541:Cystathionine beta-Synthase; C412743:OpuA protein, Lactococcus lactis