Histidine residues are important for preserving the structure and heme binding to the C-elegans HRG-3 heme-trafficking protein
Histidine residues are important for preserving the structure and heme binding to the C-elegans HRG-3 heme-trafficking protein
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DOI：
10.1007/s00775-015-1304-0
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发表时间：
2015-12-01
影响因子：
3
通讯作者：
Ruthstein, Sharon
中科院分区：
文献类型：
--
作者：
Marciano, Ortal;Moskovitz, Yoni;Ruthstein, Sharon
C.线虫是血红素营养缺陷型，需要环境血红素来维持。因此，蠕虫利用HRG-3，一种小的血红素运输蛋白，将血红素从肠运输到肠外组织和胚胎。然而，HRG-3如何结合和递送血红素仍然未知。在这项研究中，我们利用电子顺磁共振光谱与定点自旋标记，吸收光谱，圆二色性和诱变，以获得结构和分子的见解HRG-3。我们发现，HRG-3是一个二聚体，而H9和H10是重要的残基，保留了HRG-3二聚体中的特定构象状态。在没有H9和H10的情况下，HRG-3仍然可以结合血红素，尽管具有不同的亲和力。此外，血红素结合位点更靠近N-末端而不是C-末端。总之，我们的研究结果奠定了基础，为今后的机制和结构的研究HRG-3和组织间血红素贩运后生动物。
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.