核受体共激活因子 4(NCOA4)铁蛋白结合域的表达和特性。
Expression and characterization of the ferritin binding domain of Nuclear Receptor Coactivator-4 (NCOA4).
机构信息
Molecular Biology Laboratory, Department of Molecular and Translational Medicine (DMMT), University of Brescia, Viale Europa 11, Brescia, Italy.
Laboratory of Physics, Department of Molecular and Translational Medicine (DMMT), University of Brescia, Viale Europa 11, Brescia, Italy.
出版信息
Biochim Biophys Acta Gen Subj. 2017 Nov;1861(11 Pt A):2710-2716. doi: 10.1016/j.bbagen.2017.07.015. Epub 2017 Jul 25.
Ferritinophagy is the process of autophagic degradation of ferritin that participates in the regulation of cellular iron homeostasis. This process was shown to be mediated by the selective cargo-receptor Nuclear Receptor Coactivator-4 (NCOA4) that binds ferritin and targets it to emerging autophagosome. To characterize some of the biochemical properties of the interaction between the two proteins we cloned and expressed in E. coli the ferritin-binding domain of human NCOA4, fragment 383-522. It was purified and subjected to biochemical analysis. The NCOA4(383-522) fragment was expressed in soluble and dimeric form, and CD spectra indicated low level of secondary structure. The Ferritin binding activity of the fragment was investigated by developing an electrophoretic mobility shift and an ELISA assays. They showed that the NCOA4 fragment binds the H-ferritin with an affinity in the nM range, but not the R23A H-ferritin mutant and the L-ferritin chain, confirming the high specificity for the H-chain. The H-ferritin could bind up to 24 NCOA4(383-522) fragments forming highly stable and insoluble complexes. The binding was partially inhibited only by Fe(II) among the various divalent metal ions analyzed. The iron-dependent, highly-specific formation of the remarkably stable H-ferritin-NCOA4 complex shown in this work may be important for the characterization of the mechanism of ferritinophagy.
铁蛋白噬是自噬降解铁蛋白的过程,参与细胞铁稳态的调节。该过程由选择性货物受体核受体共激活因子 4(NCOA4)介导,它与铁蛋白结合并将其靶向新形成的自噬体。为了描述这两种蛋白质之间相互作用的一些生化特性,我们在大肠杆菌中克隆和表达了人 NCOA4 的铁蛋白结合域,片段 383-522。它被纯化并进行了生化分析。NCOA4(383-522)片段以可溶性和二聚体形式表达,CD 光谱表明其二级结构水平较低。通过开发电泳迁移率变化和 ELISA 测定法研究了片段的铁蛋白结合活性。结果表明,NCOA4 片段以纳摩尔级亲和力与 H-铁蛋白结合,但不与 R23A H-铁蛋白突变体和 L-铁蛋白链结合,证实了对 H-链的高特异性。H-铁蛋白最多可结合 24 个 NCOA4(383-522)片段,形成高度稳定且不溶的复合物。在分析的各种二价金属离子中,只有 Fe(II)部分抑制了结合。本研究中所示的铁依赖性、高度特异性的 H-铁蛋白-NCOA4 复合物的形成可能对铁蛋白噬的机制特征具有重要意义。