Genetic and Biochemical Studies of YqjH and YqjI: Cross-talk between Iron Homeostasis and Nickel Homeostasis in Escherichia Coli
type: CreativeWork
description: Metals are important for maintaining proper cellular functions. Cells evolved metal homeostasis systems to control metal acquisition and utilization in response to environmental changes in order to fulfill the cellular metal demand under different situations. Extensive studies have been carried out to elucidate metal homeostasis systems for individual metals. However, the cross-regulation between different metals is not well-understood. In our study, we focus on the cross-regulation of iron and nickel in bacteria by studying the yqjH-yqjI gene pair in Escherichia coli (E. coli). In E. coli, the yqjH gene encodes a putative ferric siderophore reductase that is also part of the Fur regulon. The yqjI gene, divergently transcribed from yqjH, encodes a novel member of the winged-helix family of transcriptional regulators and also contains an N-terminal extension similar to the Ni2+-binding C-terminal tail of SlyD. We found that YqjH has ferric reductase activity and is required for iron homeostasis in E. coli. In addition, elevated nickel stress levels disrupt iron homeostasis in E. coli and deletion of yqjH increases nickel toxicity. YqjI represses the expression of yqjH and its own gene, and nickel is able to reverse this inhibition effect. Purified YqjI has at least two oligomeric forms in solution (monomer, and most probably hexamer), and shows multiple oligomeric forms in the protein gel (monomer, dimer, trimer, tetramer, etc.). The interchange of the oligomeric states is regulated by oxygen but not by nickel. Only v “hexameric” apo-YqjI has DNA affinity and binding to nickel or iron reduces YqjI DNA-binding activity in vitro. The above results suggest that the YqjI protein controls expression of yqjH to help maintain iron homeostasis under conditions (such as elevated cellular nickel levels) that disrupt iron metabolism. By optimizing the protocol for fluorescence-labeled DNase I footprinting, we improved the data quality and reproducibility, which allows it to be …
abstract: Metals are important for maintaining proper cellular functions. Cells evolved metal homeostasis systems to control metal acquisition and utilization in response to environmental changes in order to fulfill the cellular metal demand under different situations. Extensive studies have been carried out to elucidate metal homeostasis systems for individual metals. However, the cross-regulation between different metals is not well-understood. In our study, we focus on the cross-regulation of iron and nickel in bacteria by studying the yqjH-yqjI gene pair in Escherichia coli (E. coli). In E. coli, the yqjH gene encodes a putative ferric siderophore reductase that is also part of the Fur regulon. The yqjI gene, divergently transcribed from yqjH, encodes a novel member of the winged-helix family of transcriptional regulators and also contains an N-terminal extension similar to the Ni2+-binding C-terminal tail of SlyD. We found that YqjH has ferric reductase activity and is required for iron homeostasis in E. coli. In addition, elevated nickel stress levels disrupt iron homeostasis in E. coli and deletion of yqjH increases nickel toxicity. YqjI represses the expression of yqjH and its own gene, and nickel is able to reverse this inhibition effect. Purified YqjI has at least two oligomeric forms in solution (monomer, and most probably hexamer), and shows multiple oligomeric forms in the protein gel (monomer, dimer, trimer, tetramer, etc.). The interchange of the oligomeric states is regulated by oxygen but not by nickel. Only v “hexameric” apo-YqjI has DNA affinity and binding to nickel or iron reduces YqjI DNA-binding activity in vitro. The above results suggest that the YqjI protein controls expression of yqjH to help maintain iron homeostasis under conditions (such as elevated cellular nickel levels) that disrupt iron metabolism. By optimizing the protocol for fluorescence-labeled DNase I footprinting, we improved the data quality and reproducibility, which allows it to be …
author: Wang, Suning
keywords: Chemistry, Physical Sciences and Mathematics
date published: 2012-01-01T08:00:00Z
date modified: 2026-07-24T04:38:31Z
provider: University of South Carolina
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of South Carolina