Miscoordination of the iron-sulfur clusters of the anaerobic transcription factor, FNR, allows simple repression but not activation

Colin Scott, Jeffrey Green*

*Corresponding author for this work

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

The FNR protein of Escherichia coli regulates target genes in response to anaerobiosis. Environmental oxygen is sensed by the acquisition of oxygen-labile [4Fe-4S] clusters that promote dimerization, DNA binding, and productive interactions with RNA polymerase. Three N-terminal cysteine residues (Cys20, Cys23, and Cys29) and Cys122 act as ligands for the FNR iron sulfur clusters. An FNR variant, FNR-C20S, that retains only trace activity in vivo can acquire [4Fe-4S] clusters in vitro that enhance site-specific DNA binding. Second site substitutions in activating regions AR1, AR2, and AR3 restore in vivo activity to FNR-C20S, suggesting that the impairment in FNR-C20S activity is due to a failure to communicate with RNA polymerase effectively. Here we show that FNR-C20S can repress a simple FNR-regulated promoter in vivo and that it can form productive heterodimers with an FNR variant with altered DNA binding specificity, FNR-E209V. Transcription studies with FNR-E209V·FNR-C20S heterodimers indicate that the presence of a miscoordinated iron-sulfur cluster (FNRC20S) in the downstream (but not the upstream) subunit of the FNR dimer impairs activation from a class II promoter and that this impairment can be overcome by amino acid substitutions known to unmask AR2 or improve AR3 in the affected subunit.

Original languageEnglish
Pages (from-to)1749-1754
Number of pages6
JournalJournal of Biological Chemistry
Volume277
Issue number3
DOIs
Publication statusPublished - 18 Jan 2002
Externally publishedYes

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