A PAS domain with an oxygen labile [4Fe-4S](2+) cluster in the oxygen sensor kinase NreB of Staphylococcus carnosus

Biochemistry. 2008 Dec 30;47(52):13921-32. doi: 10.1021/bi8014086.

Abstract

The cytoplasmic histidine sensor kinase NreB of Staphylococcus carnosus responds to O(2) and controls together with the response regulator NreC the expression of genes of nitrate/nitrite respiration. nreBC homologous genes were found in Staphylococcus strains and Bacillus clausii, and a modified form was found in some Lactobacillus strains. NreB contains a sensory domain with similarity to heme B binding PAS domains. Anaerobically prepared NreB of S. carnosus exhibited a (diamagnetic) [4Fe-4S](2+) cluster when assessed by Mossbauer spectroscopy. Upon reaction with air, the cluster was degraded with a half-life of approximately 2.5 min. No significant amounts of Mossbauer or EPR detectable intermediates were found during the decay, but magnetic Mossbauer spectra revealed formation of diamagnetic [2Fe-2S](2+) clusters. After extended exposure to air, NreB was devoid of a FeS cluster. Photoreduction with deazaflavin produced small amounts of [4Fe-4S](+), which were degraded subsequently. The magnetically perturbed Mossbauer spectrum of the [4Fe-4S](2+) cluster corroborated the S = 0 spin state and revealed uniform electric field gradient tensors of the iron sites, suggesting full delocalization of the valence electrons and binding of each of the Fe ions by four S ligands, including the ligand to the protein. Mutation of each of the four Cys residues inactivated NreB function in vivo in accordance with their role as ligands. [4Fe-4S](2+) cluster-containing NreB had high kinase activity. Exposure to air decreased the kinase activity and content of the [4Fe-4S](2+) cluster with similar half-lives. We conclude that the sensory domain of NreB represents a new type of PAS domain containing a [4Fe-4S](2+) cluster for sensing and function.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Air
  • Half-Life
  • Histidine Kinase
  • Iron-Sulfur Proteins / chemistry*
  • Magnetics
  • Oxygen / chemistry
  • Oxygen / pharmacology*
  • Protein Kinases / chemistry*
  • Spectroscopy, Mossbauer
  • Staphylococcus / enzymology*

Substances

  • Iron-Sulfur Proteins
  • Protein Kinases
  • Histidine Kinase
  • Oxygen