The ubiquitin proteasome system is critical for the regulation of protein turnover, which is implicated in the modulation of a wide array of biological processes in eukaryotes, ranging from cell senescence to virulence in plant and human hosts. Proteins to be marked for ubiquitination and subsequent degradation are bound by F-box proteins, which are interchangeable substrate-recognising receptors. These F-box proteins bind a wide range of substrates and associate with the adaptor protein Skp1 and the scaffold Cul1 to form Skp1-Cul1-F-box (SCF) complexes. SCF complex components are highly conserved in eukaryotes, ranging from yeast to humans. However, information regarding the composition of these complexes and the biological roles of F-box proteins is limited, specifically in filamentous fungal species like the genus Aspergillus. In this study, we have identified 51 and 55 fbx-encoding genes in the genomes of two pathogenic fungi, A. fumigatus and A. flavus, respectively. Immunoprecipitations of the HA-tagged SkpA adaptor protein revealed that 26 F-box proteins in A. fumigatus and 30 F-box proteins in A. flavus are involved in SCF complex formation during vegetative growth. These interactome data also revealed that a diverse array of SCF complex conformations exist in response to various exogenous stressors. Lastly, we have provided evidence that the F-box protein Fbx45 interacts with SkpA in both species in response to Amphotericin B. Orthologs of the fbx45 gene are highly conserved in Aspergillus species, but are not present within the genomes of organisms such as yeast, plants or humans. This suggests that Fbx45 could potentially be a novel F-box protein that is unique to specific filamentous fungi such as Aspergillus species.

中文翻译：

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致病曲霉中 SkpA-CulA-F-box E3 连接酶复合物的鉴定。

泛素蛋白酶体系统对于蛋白质周转的调节至关重要，蛋白质周转涉及真核生物中从细胞衰老到植物和人类宿主毒力的一系列生物过程的调节。被标记为泛素化和随后降解的蛋白质被 F-box 蛋白结合，F-box 蛋白是可互换的底物识别受体。这些 F-box 蛋白结合多种底物，并与接头蛋白 Skp1 和支架 Cul1 结合形成 Skp1-Cul1-F-box (SCF) 复合物。SCF 复杂成分在真核生物中高度保守，从酵母到人类。然而，关于这些复合物的组成和 F-box 蛋白的生物学作用的信息是有限的，特别是在丝状真菌物种中，如曲霉属。在这项研究中，我们分别在两种病原真菌 A. fumigatus 和 A. flavus 的基因组中鉴定了 51 个和 55 个 fbx 编码基因。HA 标记的 SkpA 接头蛋白的免疫沉淀显示，烟曲霉中的 26 种 F-box 蛋白和黄曲霉中的 30 种 F-box 蛋白在营养生长过程中参与了 SCF 复合物的形成。这些相互作用组数据还表明，存在多种 SCF 复杂构象以响应各种外源性压力源。最后，我们提供了证据表明 F-box 蛋白 Fbx45 与两种物种中的 SkpA 相互作用以响应两性霉素 B。 fbx45 基因的直向同源物在曲霉属物种中高度保守，但不存在于酵母等生物的基因组中，植物或人类。