orals 5th Asia-Pacific NMR Symposium 2013

Ferrous iron transporter protein C from Klebsiella pneumoniae contains a [4Fe-4S] cluster  (#77)

Kuang-Lung Hsueh 1 , Liang-Kun Yu 1 , Yung-Han Chen 2 , Ya-Hsin Cheng 1 , Yin-Cheng Hsieh 3 , Shyue-chu Ke 2 , Chun-Jung Chen 3 , Tai-huang Huang 1
  1. Academia Sinica, Taiwan
  2. Physics, National Dong Hwa University, Hualien, Taiwan
  3. Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu, Taiwan

Iron is essential for the survival, virulence, and colonization of pathogens. Feo is suggested to function as the ferrous iron (Fe2+) transporter. The enterobacterial Feo system is composed of three proteins: FeoB is the indispensable component and a large membrane protein likely to function as a permease; FeoA is a small src-homology 3 (SH3) domain protein that interacts with FeoB; In general, feo operon consists of FeoA and FeoB. In some pathogens (γ-probacteria) including Samonella (food poisoning), Escherichia coli (food poisoning), L. pneumophila (Legionnaire’s disease), Yersinia (plague), Vibrio (cholera) and Klebsiella pneumoniae (pneumonia), feo operon is composed of FeoA, FeoB and an additional FeoC. FeoC, is a winged-helix protein containing four conserved Cys residues in a sequence suitable for harboring a putative iron-sulfur (Fe-S) cluster. The presence of an iron sulfur cluster on FeoC has never been shown experimentally. We report here that under anaerobic conditions the recombinant Klebsiella pneumoniae FeoC (KpFeoC) exhibited hyperfine-shifted NMR resonances and UV-VIS absorbance spectra characteristic of a paramagnetic center. EPR and EXAFS results were consistent only with the [4Fe-4S] clusters. Substituting the cysteinyl sulfur with oxygen resulted in significantly reduced cluster stability, establishing the roles of these cysteines as the ligands for the Fe-S cluster. When exposed to oxygen, the [4Fe-4S] cluster degraded to [3Fe-4S] and eventually was lost. We propose that KpFeoC may regulate the function of Feo transporter through the oxygen and/or iron sensitive coordination of the Fe-S cluster.