A ligand-induced switch in the periplasmic domain of sensor histidine kinase CitA.
Sensor histidine kinases of two-component signal-transduction systems are essential for bacteria to adapt to variable environmental conditions. However, despite their prevalence, it is not well understood how extracellular signals such as ligand binding regulate the activity of these sensor kinases. CitA is the sensor histidine kinase in Klebsiella pneumoniae that regulates the transport and anaerobic metabolism of citrate in response to its extracellular concentration. We report here the X-ray structures of the periplasmic sensor domain of CitA in the citrate-free and citrate-bound states. A comparison of the two structures shows that ligand binding causes a considerable contraction of the sensor domain. This contraction may represent the molecular switch that activates transmembrane signaling in the receptor.
Sevvana
Madhumati
M
Department of Structural Chemistry, University of Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany.
Vijayan
Vinesh
V
Zweckstetter
Markus
M
Reinelt
Stefan
S
Madden
Dean R
DR
Herbst-Irmer
Regine
R
Sheldrick
George M
GM
Bott
Michael
M
Griesinger
Christian
C
Becker
Stefan
S
D019343:Citric Acid / Q000737:chemistry / Q000378:metabolism; D018360:Crystallography, X-Ray; D019281:Dimerization; D000071677:Histidine Kinase; D007711:Klebsiella pneumoniae / Q000201:enzymology / Q000235:genetics; D008024:Ligands; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D019897:Periplasm / Q000201:enzymology*; D011485:Protein Binding; D011494:Protein Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D040681:Structural Homology, Protein
D008024:Ligands; D019343:Citric Acid; D011494:Protein Kinases; D000071677:Histidine Kinase