Molecular and Biochemical Analysis of the Histidine Kinase CusS and its Role in Metal Resistance in Escherichia coli

Persistent Link:
http://hdl.handle.net/10150/232493
Title:
Molecular and Biochemical Analysis of the Histidine Kinase CusS and its Role in Metal Resistance in Escherichia coli
Author:
Aravind, Swapna
Issue Date:
2012
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Transition metals such as copper, zinc and nickel are required in many enzymatic processes that require redox changes. When transition metal concentration exceeds a certain threshold, their redox and metal binding properties make these elements extremely toxic. Bacteria regulate the cellular concentration of these important, yet toxic, elements using elaborate homeostatic systems. One such mechanism is the chemiosmotic extrusion of copper by the Cus system in the Gram-negative bacterium Escherichia coli. This work studies the regulation of the Cus system in response to copper and silver ions. Copper is an essential cofactor required in many enzymatic processes. But its redox properties can lead to toxicity. Silver is chemically similar to copper, but is not bioactive and its presence in cells can lead to extreme cytotoxicity. Transcription from cusCFBA genes is controlled by the CusR/CusS TCS in response to elevated levels of copper or silver in the periplasmic space of E. coli. Extracellular signals are transduced into the cell through phosphotransfer reactions between the prototypical histidine kinase CusS and the response regulator CusR. Copper sensing by the periplasmic domain of CusS is proposed to initiate signal transduction in the Cus system. Despite the frequency with which bacteria employ histidine kinases to sense their environment, signal recognition and incorporation by the protein is not well understood. The goal of this research is to investigate the role of CusS in regulating metal homeostasis in E. coli and characterize the periplasmic domain of the protein to determine its metal binding properties. The experiments described in this work reveal that the CusS is essential for copper and silver resistance and regulates expression from the cusCFBA promoter region. Signal recognition occurs by direct metal binding by the periplasmic domain of CusS. Metal binding causes a change in the secondary structure of the domain and its tendency to dimerize is enhanced under these conditions. The possibility of signal attenuation by interaction with the metallochaperone CusF is also discussed. These data help construct a model for signal transduction in the Cus system and help characterize, for the first time, a metal-responsive sensor histidine kinase in E. coli.
Type:
text; Electronic Dissertation
Keywords:
Cus system; Histidine kinase; Sensor domain; Silver; Biochemistry & Molecular Biophysics; Copper; CusR/CusS
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Biochemistry & Molecular Biophysics
Degree Grantor:
University of Arizona
Advisor:
McEvoy, Megan M.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleMolecular and Biochemical Analysis of the Histidine Kinase CusS and its Role in Metal Resistance in Escherichia colien_US
dc.creatorAravind, Swapnaen_US
dc.contributor.authorAravind, Swapnaen_US
dc.date.issued2012-
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractTransition metals such as copper, zinc and nickel are required in many enzymatic processes that require redox changes. When transition metal concentration exceeds a certain threshold, their redox and metal binding properties make these elements extremely toxic. Bacteria regulate the cellular concentration of these important, yet toxic, elements using elaborate homeostatic systems. One such mechanism is the chemiosmotic extrusion of copper by the Cus system in the Gram-negative bacterium Escherichia coli. This work studies the regulation of the Cus system in response to copper and silver ions. Copper is an essential cofactor required in many enzymatic processes. But its redox properties can lead to toxicity. Silver is chemically similar to copper, but is not bioactive and its presence in cells can lead to extreme cytotoxicity. Transcription from cusCFBA genes is controlled by the CusR/CusS TCS in response to elevated levels of copper or silver in the periplasmic space of E. coli. Extracellular signals are transduced into the cell through phosphotransfer reactions between the prototypical histidine kinase CusS and the response regulator CusR. Copper sensing by the periplasmic domain of CusS is proposed to initiate signal transduction in the Cus system. Despite the frequency with which bacteria employ histidine kinases to sense their environment, signal recognition and incorporation by the protein is not well understood. The goal of this research is to investigate the role of CusS in regulating metal homeostasis in E. coli and characterize the periplasmic domain of the protein to determine its metal binding properties. The experiments described in this work reveal that the CusS is essential for copper and silver resistance and regulates expression from the cusCFBA promoter region. Signal recognition occurs by direct metal binding by the periplasmic domain of CusS. Metal binding causes a change in the secondary structure of the domain and its tendency to dimerize is enhanced under these conditions. The possibility of signal attenuation by interaction with the metallochaperone CusF is also discussed. These data help construct a model for signal transduction in the Cus system and help characterize, for the first time, a metal-responsive sensor histidine kinase in E. coli.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectCus systemen_US
dc.subjectHistidine kinaseen_US
dc.subjectSensor domainen_US
dc.subjectSilveren_US
dc.subjectBiochemistry & Molecular Biophysicsen_US
dc.subjectCopperen_US
dc.subjectCusR/CusSen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineBiochemistry & Molecular Biophysicsen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorMcEvoy, Megan M.en_US
dc.contributor.committeememberCordes, Matthew H. J.en_US
dc.contributor.committeememberMontfort, William R.en_US
dc.contributor.committeememberTax, Frans E.en_US
dc.contributor.committeememberMcEvoy, Megan M.en_US
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