From signal perception to signal transduction: ligand-induced dimeric switch of DctB sensory domain in solution.
Sinorhizobium meliloti DctB is a typical transmembrane sensory histidine kinase, which senses C(4)-dicarboxylic acids (DCA) and regulates the expression of DctA, the DCA transporter. We previously reported the crystal structures of its periplasmic sensory domain (DctBp) in apo and succinate-bound states, and these structures showed dramatic conformational changes at dimeric level. Here we show a ligand-induced dimeric switch in solution and a strong correlation between DctBp's dimerization states and the in vivo activities of DctB. Using site-directed mutagenesis, we identify important determinants for signal perception and transduction. Specifically, we show that the ligand-binding pocket is essential for DCA-induced 'on' activity of DctB. Mutations at different sections of DctBp's dimerization interface can lock full-length DctB at either 'on' or 'off' state, independent of ligand binding. Taken together, these results suggest that DctBp's signal perception and transduction occur through a 'ligand-induced dimeric switch', in which the changes in the dimeric conformations upon ligand binding are responsible for the signal transduction in DctB.
National Laboratory of Protein Engineering and Plant Genetic Engineering, College of Life Sciences, Peking University, Beijing, China.
Beiyan
B
Nan
Xin
X
Liu
Yanfeng
Y
Zhou
Jiwei
J
Liu
Le
L
Zhang
Jin
J
Wen
Xiaodong
X
Zhang
Xiao-Dong
XD
Su
Yi-Ping
YP
Wang
D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D029382:Dicarboxylic Acid Transporters / Q000235:genetics / Q000378:metabolism*; D003998:Dicarboxylic Acids / Q000378:metabolism; D019281:Dimerization; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D016962:Sinorhizobium meliloti / Q000235:genetics / Q000502:physiology*
D001426:Bacterial Proteins; D029382:Dicarboxylic Acid Transporters; D003998:Dicarboxylic Acids; D050505:Mutant Proteins; C073787:DCTB protein, Sinorhizobium