Transmembrane signal transduction and osmoregulation in Escherichia coli. Functional importance of the periplasmic domain of the membrane-located protein kinase, EnvZ

• Published in: The Journal of biological chemistry Vol. 266; no. 11; pp. 6780 - 6785
• Main Authors: Tokishita, S, Kojima, A, Aiba, H, Mizuno, T
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 15.04.1991; American Society for Biochemistry and Molecular Biology
• Subjects: Bacterial Outer Membrane Proteins - genetics; Bacterial Outer Membrane Proteins - metabolism; Base Sequence; beta-Galactosidase - genetics; beta-Galactosidase - metabolism; Biological and medical sciences; Cell Membrane - physiology; Cell physiology; DNA, Bacterial - genetics; DNA, Bacterial - isolation & purification; EnvZ protein; Escherichia coli - genetics; Escherichia coli - physiology; Escherichia coli Proteins; Fundamental and applied biological sciences. Psychology; Genes, Bacterial; Kinetics; Models, Biological; Molecular and cellular biology; Molecular Sequence Data; Multienzyme Complexes; Oligonucleotide Probes; Osmolar Concentration; osmoregulation; Plasmids; Protein Kinases - genetics; Recombinant Fusion Proteins - metabolism; Restriction Mapping; Signal Transduction; Transmembrane protein; Signal transduction; Phenotype; Protein kinase; Escherichia coli; Blotting assay; Deletion; Osmoregulation; Bacteria; Kinetics; Mechanism of action; Enterobacteriaceae
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(20)89568-4

The EnvZ protein is presumably a membrane-located osmotic sensor which is involved in expression of the ompF and ompC genes in Escherichia coli. Previously, we developed an in vitro method for analyzing the intact form of the EnvZ protein located in isolated cytoplasmic membranes, and demonstrated that this particular form of the EnvZ protein exhibits the ability not only as to OmpR phosphorylation but also OmpR dephosphorylation. In this study, to gain an insight into the structural and functional importance of the putative periplasmic domain of the EnvZ protein, a set of mutant EnvZ proteins, which lack various portions of the periplasmic domain, were characterized in terms of not only their in vivo osmoregulatory phenotypes but also in vitro EnvZ-OmpR phosphotransfer reactions. It was revealed that these deletion mutant EnvZ proteins are normally incorporated into the cytoplasmic membrane. Cells harboring these mutant EnvZ proteins showed a pleiotropic phenotype, namely, OmpF- Mal- LamB- PhoA-, and produced the OmpC protein constitutively irrespective of the medium osmolarity. It was also suggested that all of these mutant EnvZ proteins were defective in their in vitro OmpR dephosphorylation ability, while their OmpR phosphorylation ability remained unaffected. These results imply the functional importance of the periplasmic domain of the EnvZ protein for modulation of the kinase/phosphatase activity exhibited by the cytoplasmic domain in response to an environmental osmotic stimulus.