Title of article :
Ligand-induced Conformational Changes in the Bacillus subtilis Chemoreceptor McpB Determined by Disulfide Crosslinking in vivo
Author/Authors :
Hendrik Szurmant، نويسنده , , Michael W. Bunn، نويسنده , , Stephen H. Cho، نويسنده , , George W. Ordal، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2004
Abstract :
Previously, we characterized the organization of the transmembrane (TM) domain of the Bacillus subtilis chemoreceptor McpB using disulfide crosslinking. Cysteine residues were engineered into serial positions along the two helices through the membrane, TM1 and TM2, as well as double mutants in TM1 and TM2, and the extent of crosslinking determined to characterize the organization of the TM domain. In this study, the organization of the TM domain was studied in the presence and absence of ligand to address what ligand-induced structural changes occur. We found that asparagine caused changes in crosslinking rate on all residues along the TM1–TM1′ helical interface, whereas the crosslinking rate for almost all residues along the TM2–TM2′ interface did not change. These results indicated that helix TM1 rotated counterclockwise and that TM2 did not move in respect to TM2′ in the dimer on binding asparagine. Interestingly, intramolecular crosslinking of paired substitutions in 34/280 and 38/273 were unaffected by asparagine, demonstrating that attractant binding to McpB did not induce a “piston-like” vertical displacement of TM2 as seen for Trg and Tar in Escherichia coli. However, these paired substitutions produced oligomeric forms of receptor in response to ligand. This must be due to a shift of the interface between different receptor dimers, within previously suggested trimers of dimers, or even higher order complexes.
Keywords :
chemotaxis , Receptor , conformational change , Disulfide crosslinking
Journal title :
Journal of Molecular Biology
Journal title :
Journal of Molecular Biology