Intermolecular complementation between two defective mutant signal-transducing receptors of Escherichia coli.
Taz1 is a hybrid signal-transducing membrane receptor between Tar, an aspartate chemoreceptor, and EnvZ, an osmosensor of Escherichia coli that is able to induce ompC expression by phosphorylating OmpR (a transcriptional activator) in response to aspartate. When the Taz1 His-277, the proposed autophosphorylation site in the cytoplasmic EnvZ domain, was replaced with a valine residue, the mutant Taz1 was unable to induce ompC expression. Similarly, when approximately two-thirds of the EnvZ domain was deleted, Taz1 was nonfunctional. However, when these two defective Taz1 proteins were coexpressed in a cell, ompC was constitutively expressed. Coinciding with this result, two mutant Taz1 molecules were able to intermolecularly complement each other to restore the OmpR kinase activity but not phosphatase activity in vitro. The identical result was also obtained with EnvZ. The present results suggest that the autophosphorylation of Taz1 and EnvZ is an intermolecular phosphorylation reaction, requiring formation of a dimer (or oligomer), and that ligand-dependent ompC expression requires not only kinase but also phosphatase activity.
Yang
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Y
Department of Biochemistry, University of Medicine and Dentistry of New Jersey, Rutgers-Robert Wood Johnson Medical School, Piscataway 08854.
Inouye
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M
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002872:Chromosome Deletion; D004926:Escherichia coli / Q000235:genetics* / Q000502:physiology; D029968:Escherichia coli Proteins; D005816:Genetic Complementation Test; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes; D016297:Mutagenesis, Site-Directed; D010749:Phosphoprotein Phosphatases / Q000235:genetics*; D010766:Phosphorylation; D010957:Plasmids; D011494:Protein Kinases; D015398:Signal Transduction
D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D009097:Multienzyme Complexes; C072091:Taz1 protein, E coli; D011494:Protein Kinases; C057843:envZ protein, E coli; D010749:Phosphoprotein Phosphatases