The transmembrane domains of the sensor kinase KdpD of Escherichia coli are not essential for sensing K+ limitation.
The sensor kinase/response regulator system KdpD/KdpE of Escherichia coli regulates the expression of the kdpFABC operon, which encodes the high affinity K+ transport system KdpFABC. The membrane-bound sensor kinase KdpD consists of four transmembrane domains, a large cytoplasmic N-terminal domain and a cytoplasmic C-terminal transmitter domain. To elucidate the role of the four transmembrane domains, various deletions were introduced in kdpD and the activities of the resulting truncated derivatives of KdpD were determined. A KdpD protein lacking all four transmembrane domains was able to sense low K+ concentrations, whereas at higher K+ concentrations kdpFABC expression was constitutive. These and further results with various truncated KdpD proteins lacking distinct parts of the transmembrane domains or derivatives in which a linker peptide or two transmembrane domains of PutP, the Na+/proline transporter of Escherichia coli, replaced the missing part indicated that the transmembrane domains are not essential for sensing of K+ limitation, but may be important for the correct positioning of the large N- and C-terminal cytoplasmic domains to each other.
Heermann
Ralf
R
Universität Osnabrück, Fachbereich/Chemie, Abteilung Mikrobiologie, Osnabrück, Germany.
Fohrmann
Andy
A
Altendorf
Karlheinz
K
Jung
Kirsten
K
D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D003593:Cytoplasm; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010766:Phosphorylation; D011188:Potassium / Q000378:metabolism*; D011494:Protein Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C489580:KdpD protein, E coli; D011494:Protein Kinases; C075616:kdpD protein, Bacteria; D010744:Phosphoric Monoester Hydrolases; D011188:Potassium