Title |
Histidine residues are important for preserving the structure and heme binding to the C. elegans HRG-3 heme-trafficking protein
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Published in |
JBIC Journal of Biological Inorganic Chemistry, November 2015
|
DOI | 10.1007/s00775-015-1304-0 |
Pubmed ID | |
Authors |
Ortal Marciano, Yoni Moskovitz, Iqbal Hamza, Sharon Ruthstein |
Abstract |
C. elegans is a heme auxotroph that requires environmental heme for sustenance. As such, worms utilize HRG-3, a small heme-trafficking protein, to traffic heme from the intestine to extra-intestinal tissues and embryos. However, how HRG-3 binds and delivers heme remains unknown. In this study, we utilized electron paramagnetic resonance spectroscopy together with site-directed spin labeling, absorption spectroscopy, circular dichroism, and mutagenesis to gain structural and molecular insights into HRG-3. We showed that HRG-3 is a dimer, whereas H9 and H10 are significant residues that preserve a specific conformational state in the HRG-3 dimer. In the absence of H9 and H10, HRG-3 can still bind heme, although with a different affinity. Furthermore, the heme-binding site is closer to the N-termini than to the C-termini. Taken together, our results lay the groundwork for future mechanistic and structural studies of HRG-3 and inter-tissue heme trafficking in metazoans. |
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