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Nitrosylation of Nitric-Oxide-Sensing Regulatory Proteins Containing [4Fe-4S] Clusters Gives Rise to Multiple Iron-Nitrosyl Complexes.

  • Author(s): Serrano, Pauline N
  • Wang, Hongxin
  • Crack, Jason C
  • Prior, Christopher
  • Hutchings, Matthew I
  • Thomson, Andrew J
  • Kamali, Saeed
  • Yoda, Yoshitaka
  • Zhao, Jiyong
  • Hu, Michael Y
  • Alp, Ercan E
  • Oganesyan, Vasily S
  • Le Brun, Nick E
  • Cramer, Stephen P
  • et al.
Abstract

The reaction of protein-bound iron-sulfur (Fe-S) clusters with nitric oxide (NO) plays key roles in NO-mediated toxicity and signaling. Elucidation of the mechanism of the reaction of NO with DNA regulatory proteins that contain Fe-S clusters has been hampered by a lack of information about the nature of the iron-nitrosyl products formed. Herein, we report nuclear resonance vibrational spectroscopy (NRVS) and density functional theory (DFT) calculations that identify NO reaction products in WhiD and NsrR, regulatory proteins that use a [4Fe-4S] cluster to sense NO. This work reveals that nitrosylation yields multiple products structurally related to Roussin's Red Ester (RRE, [Fe2 (NO)4 (Cys)2 ]) and Roussin's Black Salt (RBS, [Fe4 (NO)7 S3 ]. In the latter case, the absence of 32 S/34 S shifts in the Fe-S region of the NRVS spectra suggest that a new species, Roussin's Black Ester (RBE), may be formed, in which one or more of the sulfide ligands is replaced by Cys thiolates.

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