Crystal structures of the NO sensor NsrR reveal how its iron-sulfur cluster modulates DNA binding.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 28425466.
- Also identified by DOI 10.1038/ncomms15052 and PMC identifier 5411485.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
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.
Medical subject headings
- Bacterial Proteins
- DNA
- DNA-Binding Proteins
- Iron-Sulfur Proteins
- Nitric Oxide
- Transcription Factors