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.
Nan
Beiyan
B
National Laboratory of Protein Engineering and Plant Genetic Engineering, College of Life Sciences, Peking University, Beijing, China.
Liu
Xin
X
Zhou
Yanfeng
Y
Liu
Jiwei
J
Zhang
Le
L
Wen
Jin
J
Zhang
Xiaodong
X
Su
Xiao-Dong
XD
Wang
Yi-Ping
YP
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