Isolation and molecular characterization of the locked-on mutant of Mg2+ sensor PhoQ in Escherichia coli.
A Mg(2+) sensor mutant (PhoQD179L(A)) in which D179 of PhoQ was changed into L or A was isolated and characterized in Escherichia coli. PhoQ-PhoP regulon genes, phoPQ, mgtA and mgrB transcriptions were repressed at a high Mg(2+) concentration in WQ3007 (phoQ-defective strain)/pHO119, but not in WQ3007/pHO179L(A). The in vitro autophosphorylation activity of membrane-bound PhoQ was repressed by Mg(2+) (10 mM), but that of membrane-bound PhoQD179L(A) was not. Furthermore, the phosphotransfer from membrane-bound PhoQ to PhoP was also repressed by Mg(2+), but was not observed in membrane-bound PhoQD179L(A). These results suggest that PhoQD179L(A) is a locked-on mutant that is defective in extracellular Mg(2+)-sensing and that the D179 amino acid residue of PhoQ plays an essential role in signal transfer between the Mg(2+)-sensory and histidine kinase domain of PhoQ.
Minagawa
Shu
S
Department of Bioscience and Biotechnology, Graduate School of Agriculture, Kinki University, 3327-204 Nakamachi, Nara 631-8505, Japan.
Okura
Ryouta
R
Tsuchitani
Hiroki
H
Hirao
Kiyo
K
Yamamoto
Kaneyoshi
K
Utsumi
Ryutaro
R
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D008274:Magnesium / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009154:Mutation; D010766:Phosphorylation / Q000187:drug effects; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C465562:PhoP protein, E coli; C079792:PhoQ protein, Bacteria; D008274:Magnesium