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The transmembrane domains of the sensor kinase KdpD of Escherichia coli are not essential for sensing K + limitation
Author(s) -
Heermann Ralf,
Fohrmann Andy,
Altendorf Karlheinz,
Jung Kirsten
Publication year - 2003
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2003.03348.x
Subject(s) - biology , escherichia coli , transmembrane protein , transmembrane domain , kinase , computational biology , microbiology and biotechnology , biochemistry , membrane , gene , receptor
Summary 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.