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Assignment of the zinc ligands in RsrA, a redox-sensing ZAS protein from Streptomyces coelicolor.

journal contribution
posted on 2023-06-08, 05:46 authored by Konrad Zdanowski, Phillip Doughty, Piotr Jakimowicz, Liisa O'Hara, Mark J Buttner, Mark PagetMark Paget, Colin Kleanthous
ZAS proteins are widespread bacterial zinc-containing anti-sigma factors that regulate the activity of sigma factors in response to diverse cues. One of the best characterized ZAS proteins is RsrA from Streptomyces coelicolor, which responds to disulfide stress. Zn-RsrA binds and represses the transcriptional activity of sR in the reducing environment of the cytoplasm but undergoes reversible, intramolecular disulfide bond formation during oxidative stress. This expels the single metal ion and causes dramatic structural changes in RsrA that result in its dissociation from sR, leaving the sigma factor free to activate the transcription of antioxidant genes. We showed recently that Zn2+ serves a critical role in modulating the redox activity of RsrA thiols but uncertainty remains as to how the metal ion is coordinated in RsrA and related ZAS proteins. Using a combination of random and site-specific mutagenesis with zinc K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy, we have assigned unambiguously the metal ligands in RsrA, thereby distinguishing between the different ligation models that have been proposed. The data show that the zinc site in RsrA is comprised of Cys11, His37, Cys41, and Cys44. Three of these residues are part of a conserved ZAS-specific sequence motif (H37xxxC41xxC44), with the fourth ligand, Cys11, found in a subset of ZAS proteins. Cys11 and Cys44 form the trigger disulfide in RsrA, explaining why the metal ion is expelled during oxidation. We discuss these data in the context of redox sensing by RsrA and the sensory mechanisms of other ZAS proteins.

History

Publication status

  • Published

Journal

Biochemistry

ISSN

0006-2960

Issue

27

Volume

45

Page range

8294¿8300

Pages

7.0

Department affiliated with

  • Biochemistry Publications

Full text available

  • No

Peer reviewed?

  • Yes

Legacy Posted Date

2012-02-06

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