Chaperone Function in Iron-Sulfur Protein Folding

描述（由申请人提供）：含铁硫簇的蛋白质具有重要的电子转移、催化和调节功能，但形成Fe-S簇并将其引入蛋白质的细胞机制尚未完全了解。最近的研究已经确定了参与Fe-S蛋白生物合成的新蛋白，并且正在定义它们的作用和相互作用。在细菌中，这些蛋白质中的几种被编码在保守的基因簇中，该基因簇编码三种Fe-S簇组装组分（IscS、IscU、IscA）和专门的伴侣/共伴侣系统（HscA和HscB）。我们已经产生了重组形式的这些蛋白质从大肠杆菌，并提出了生化，生物物理和结构的研究，以调查他们的角色在组装的Fe-S-集群和纳入的Fe-S集群到蛋白质。 本研究将探讨硫从半胱氨酸脱硫酶IscS转移到瞬时Fe-S支架蛋白IscU的机制，IscA在铁结合和簇组装中的作用，IscU与HscA/HscB分子伴侣系统的相互作用，以及Fe-S簇向受体脱辅基蛋白的转移。HscA与肽的相互作用的其他研究也将进行调查热休克蛋白70底物相互作用的一般原则。 这些研究结果将提供一个更好的理解的分子机制参与的Fe-S蛋白的生物合成。此外，Fe-S蛋白组装的类似保守机制发生在真核生物中，这些发现可能为人类疾病的分子基础提供见解，例如与线粒体肌病相关的疾病。

DESCRIPTION (provided by applicant): Proteins containing iron-sulfur clusters possess important electron transfer, catalytic, and regulatory functions, but the cellular mechanisms by which the Fe-S clusters are formed and introduced into proteins are not well understood. Recent studies have identified novel proteins that participate in Fe-S protein biosynthesis, and their roles and interactions are being defined. In bacteria several of these proteins are encoded in a conserved gene cluster that encodes three Fe-S cluster assembly components (IscS, IscU, IscA), and a specialized chaperone/co-chaperone system (HscA and HscB). We have produced recombinant forms of each of these proteins from Escherichia coli, and propose biochemical, biophysical and structural studies to investigate their roles in the assembly of Fe-S-clusters and the incorporation of Fe-S clusters into proteins. The proposed studies will address 1) the mechanism of transfer of sulfur from the cysteine desulfurase IscS to the transient Fe-S scaffold protein IscU, 2) the role of IscA in iron binding and cluster assembly, 3) interactions of IscU with the HscA/HscB chaperone system, and 4) the transfer of Fe-S clusters to acceptor apo-proteins. Additional studies on the interaction of HscA with peptides will also be carried out to investigate general principles of hsp70-substrate interactions. Results of these studies will provide a better understanding of molecular mechanisms involved in the biogenesis of Fe-S proteins. Furthermore, a similar conserved mechanism of Fe-S protein assembly occurs in eukaryotes, and the findings may provide insight into the molecular basis of human diseases such as those associated with mitochondrial myopathies.