Ca2+-enhanced phosphorylation of a chimeric protein kinase involved with bacterial signal transduction

A. Rampersaud, R. Utsumi, J. Delgado, S. A. Forst, Masayori Inouye

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

The Tar-EnvZ hybrid molecule (Taz1) is an inner membrane transducer that activates OmpR, a transcriptional activator for porin gene expression (ompC), in response to an aspartic acid signal. Signal transduction by Taz1 most likely involves a phosphorylated Taz1 intermediate that donates its phosphate to OmpR. Phosphorylated OmpR has already been implicated in transcriptional activation of porin genes. Using a cell-free system containing Taz1-enriched membrane fractions, we have examined the phosphorylation properties of Taz1 and the stimulatory effects of divalent and monovalent ions. Highest activation of Taz1 phosphorylation was observed with CaCl2, and its stimulation could be observed with as low as 60 μM of CaCl2. Phosphorylated Taz1 could readily donate its phosphate group to OmpR in the presence of calcium. CaCl2 was also able to enhance phosphorylation of intact membrane-bound EnvZ and a cytoplasmic fragment of EnvZ lacking the receptor and transmembrane domains. These results indicate that the site for CaCl2 stimulation is within the cytoplasmic region of EnvZ and probably involves an enhanced rate of EnvZ phosphorylation.

Original languageEnglish (US)
Pages (from-to)7633-7637
Number of pages5
JournalJournal of Biological Chemistry
Volume266
Issue number12
StatePublished - Jul 22 1991

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Signal transduction
Phosphorylation
Protein Kinases
Signal Transduction
Porins
Membranes
Chemical activation
Phosphates
Tars
Cell-Free System
Transducers
Gene expression
Aspartic Acid
Transcriptional Activation
Genes
Ions
Calcium
Gene Expression
Molecules

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Rampersaud, A. ; Utsumi, R. ; Delgado, J. ; Forst, S. A. ; Inouye, Masayori. / Ca2+-enhanced phosphorylation of a chimeric protein kinase involved with bacterial signal transduction. In: Journal of Biological Chemistry. 1991 ; Vol. 266, No. 12. pp. 7633-7637.
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Ca2+-enhanced phosphorylation of a chimeric protein kinase involved with bacterial signal transduction. / Rampersaud, A.; Utsumi, R.; Delgado, J.; Forst, S. A.; Inouye, Masayori.

In: Journal of Biological Chemistry, Vol. 266, No. 12, 22.07.1991, p. 7633-7637.

Research output: Contribution to journalArticle

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AB - The Tar-EnvZ hybrid molecule (Taz1) is an inner membrane transducer that activates OmpR, a transcriptional activator for porin gene expression (ompC), in response to an aspartic acid signal. Signal transduction by Taz1 most likely involves a phosphorylated Taz1 intermediate that donates its phosphate to OmpR. Phosphorylated OmpR has already been implicated in transcriptional activation of porin genes. Using a cell-free system containing Taz1-enriched membrane fractions, we have examined the phosphorylation properties of Taz1 and the stimulatory effects of divalent and monovalent ions. Highest activation of Taz1 phosphorylation was observed with CaCl2, and its stimulation could be observed with as low as 60 μM of CaCl2. Phosphorylated Taz1 could readily donate its phosphate group to OmpR in the presence of calcium. CaCl2 was also able to enhance phosphorylation of intact membrane-bound EnvZ and a cytoplasmic fragment of EnvZ lacking the receptor and transmembrane domains. These results indicate that the site for CaCl2 stimulation is within the cytoplasmic region of EnvZ and probably involves an enhanced rate of EnvZ phosphorylation.

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