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Nat Commun. 2017 Apr 20;8:15052. doi: 10.1038/ncomms15052.

Crystal structures of the NO sensor NsrR reveal how its iron-sulfur cluster modulates DNA binding.

Author information

1
Metalloproteins Unit, Institut de Biologie Structurale, CEA, CNRS, Université Grenoble-Alpes, 71, avenue des Martyrs, CS 10090, 38044 Grenoble cedex 9, France.
2
Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.
3
School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.

Abstract

NsrR from Streptomyces coelicolor (Sc) regulates the expression of three genes through the progressive degradation of its [4Fe-4S] cluster on nitric oxide (NO) exposure. We report the 1.95 Å resolution crystal structure of dimeric holo-ScNsrR and show that the cluster is coordinated by the three invariant Cys residues from one monomer and, unexpectedly, Asp8 from the other. A cavity map suggests that NO displaces Asp8 as a cluster ligand and, while D8A and D8C variants remain NO sensitive, DNA binding is affected. A structural comparison of holo-ScNsrR with an apo-IscR-DNA complex shows that the [4Fe-4S] cluster stabilizes a turn between ScNsrR Cys93 and Cys99 properly oriented to interact with the DNA backbone. In addition, an apo ScNsrR structure suggests that Asn97 from this turn, along with Arg12, which forms a salt-bridge with Asp8, are instrumental in modulating the position of the DNA recognition helix region relative to its major groove.

PMID:
28425466
PMCID:
PMC5411485
DOI:
10.1038/ncomms15052
[Indexed for MEDLINE]
Free PMC Article

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