7txn

Reduced Structure of RexT

spinqualitylabelsall models 7txn, resolution 1.95Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 7txn is a 2 chain structure with sequence from Nostoc sp. PCC 7120 = FACHB-418. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.95Å Ligands: CL, GOL Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function Q8YVV6_NOSS1 Publication Abstract from PubMed Organisms have a myriad of strategies for sensing, responding to, and combating reactive oxygen species, which are unavoidable consequences of aerobic life. In the heterocystous cyanobacterium Nostoc sp. PCC 7120, one such strategy is the use of an ArsR-SmtB transcriptional regulator RexT that senses H2O2 and upregulates expression of thioredoxin to maintain cellular redox homeostasis. Different from many other members of the ArsR-SmtB family which bind metal ions, RexT has been proposed to use disulfide bond formation as a trigger to bind and release DNA. Here, we present high-resolution crystal structures of RexT in the reduced and H2O2-treated states. These structures reveal that RexT showcases the ArsR-SmtB winged-helix-turn-helix fold and forms a vicinal disulfide bond to orchestrate a response to H2O2. The importance of the disulfide-forming Cys residues was corroborated using site-directed mutagenesis, mass spectrometry, and H2O2-consumption assays. Furthermore, an entrance channel for H2O2 was identified and key residues implicated in H2O2 activation were pinpointed. Finally, bioinformatics analysis of the ArsR-SmtB family indicates that the vicinal disulfide "redox switch" is a unique feature of cyanobacteria in the Nostocales order, presenting an interesting case where an ArsR-SmtB protein scaffold has been evolved to showcase peroxidatic activity and facilitate redox-based regulation. Structural and mechanistic basis for redox sensing by the cyanobacterial transcription regulator RexT.,Li B, Jo M, Liu J, Tian J, Canfield R, Bridwell-Rabb J Commun Biol. 2022 Mar 28;5(1):275. doi: 10.1038/s42003-022-03226-x. PMID:35347217 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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