Homeostasis of transition metals is necessary to maintain vital functions such as respiration while avoiding toxic accumulation of metals. While nickel is an essential metal for anaerobic growth in E. coli, under aerobic conditions nickel can target zinc and iron metabolism. We showed previously that the ferric siderophore reductase YqjH plays a role in iron homeostasis under nickel stress and is part of the ferric uptake regulator (Fur) regulon. The yqjH gene also is divergently transcribed from yqjI. YqjI functions as a transcriptional regulator by inhibiting the transcription of both yqjH and yqjI promoters via their shared intergenic region. YqjI-dependent transcriptional repression is partially relieved under nickel stress in vivo. We have mutated the yqjH – yqjI intergenic region to identify important regulatory features of the two promoters. YqjI’s N-terminus also is homologous to the nickel binding domains of the SlyD and RcnA proteins, suggesting this protein domain directly senses nickel. We have utilized site directed mutagenesis coupled with a combination of genetic, biochemical, and biophysical approaches to characterize nickel-dependent control of YqjI DNA binding. Our studies provide molecular insight into the mechanism of this novel metalloregulatory protein.

Siderophore-mediated iron acquisition during nickel stress is controlled by the metalloregulatory protein YqjI in E. coli

251st National Meeting (2016)

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