Chaperone Function in Iron-Sulfur Protein Folding

描述(申请人提供)：含有铁-硫簇的蛋白质具有重要的电子转移、催化和调节功能，但铁-S簇形成和引入蛋白质的细胞机制尚不清楚。最近的研究发现了参与铁-S蛋白生物合成的新蛋白，并正在确定它们的作用和相互作用。在细菌中，这些蛋白质中的一些被编码在一个保守的基因簇中，该基因簇编码三个Fe-S簇组装组件(IscS、IscU、IscA)和一个专门的伴侣/辅伴侣系统(HscA和HscB)。我们已经从大肠杆菌中获得了这些蛋白的重组形式，并提出了生化、生物物理和结构研究，以探讨它们在Fe-S-簇组装和Fe-S簇掺入蛋白质中的作用。 这些研究将涉及1)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，2)IscA在铁结合和簇组装中的作用，3)IscU与HscA/HscB伴侣系统的相互作用，以及4)Fe-S簇转移到受体脱辅基蛋白。此外，还将开展HSCA与多肽相互作用的其他研究，以探讨HSP70与底物相互作用的一般原理。 这些研究结果将为更好地理解铁-S蛋白生物发生的分子机制提供依据。此外，铁-S蛋白组装的类似保守机制也存在于真核生物中，这一发现可能为深入了解人类疾病的分子基础，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.