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Proc Natl Acad Sci U S A. 2009 Nov 24;106(47):19753-60. doi: 10.1073/pnas.0911645106. Epub 2009 Nov 16.

A structural basis for H-NOX signaling in Shewanella oneidensis by trapping a histidine kinase inhibitory conformation.

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Department of Chemistry, University of California, Berkeley, CA 94720-3220, USA.


Heme nitric oxide/oxygen (H-NOX) proteins are found in eukaryotes where they are typically part of a larger protein such as soluble guanylate cyclase and in prokaryotes where they are often found in operons with a histidine kinase, suggesting that H-NOX proteins serve as sensors for NO and O(2) in signaling pathways. The Fe(II)-NO complex of the H-NOX protein from Shewanella oneidensis inhibits the autophosphorylation of the operon-associated histidine kinase, whereas the ligand-free H-NOX has no effect on the kinase. NMR spectroscopy was used to determine the structures of the Fe(II)-CO complex of the S. oneidensis H-NOX and the Fe(II)-CO complex of the H103G H-NOX mutant as a mimic of the ligand-free and kinase-inhibitory Fe(II)-NO H-NOX, respectively. The results provide a molecular glimpse into the ligand-induced conformational changes that may underlie kinase inhibition and the subsequent control of downstream signaling.

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