https://ror.org/03bnmw459 Institute of Biochemistry and Biology, Department of Biochemistry, University of Potsdam, Potsdam-Golm, Germany.
https://ror.org/00rcxh774 Institute for Genetics, Center of Molecular Biosciences, Department of Biology, Faculty of Mathematics and Natural Sciences, University of Cologne, Cologne, Germany.
Life Sci Alliance. 2024 Sep 11;7(11). doi: 10.26508/lsa.202402865. Print 2024 Nov.
The yeast (β4-S142F) mutant accumulates late 20S proteasome core particle precursor complexes (late-PCs). We report a 2.1 Å cryo-EM structure of this intermediate with full-length Ump1 trapped inside, and Pba1-Pba2 attached to the α-ring surfaces. The structure discloses intimate interactions of Ump1 with β2- and β5-propeptides, which together fill most of the antechambers between the α- and β-rings. The β5-propeptide is unprocessed and separates Ump1 from β6 and β7. The β2-propeptide is disconnected from the subunit by autocatalytic processing and localizes between Ump1 and β3. A comparison of different proteasome maturation states reveals that maturation goes along with global conformational changes in the rings, initiated by structuring of the proteolytic sites and their autocatalytic activation. In the strain, β2 is activated first enabling processing of β1-, β6-, and β7-propeptides. Subsequent maturation of β5 and β1 precedes degradation of Ump1, tightening of the complex, and finally release of Pba1-Pba2.
酵母（β4-S142F）突变体积累晚期 20S 蛋白酶体核心颗粒前体复合物（晚期-PC）。我们报告了该中间产物的 2.1 Å 冷冻电镜结构，其中全长 Ump1 被困在里面，Pba1-Pba2 附着在α环表面。该结构揭示了 Ump1 与β2-和β5-前肽之间的密切相互作用，它们共同填充了α-和β-环之间的大部分前腔室。β5-前肽未加工，将 Ump1 与β6 和β7 分开。β2-前肽通过自催化加工与亚基断开，并位于 Ump1 和β3 之间。不同蛋白酶体成熟状态的比较表明，成熟伴随着环的全局构象变化，这是由蛋白酶位点的结构和自催化激活引发的。在 菌株中，β2 首先被激活，从而使β1-、β6-和β7-前肽发生加工。随后β5 和β1 的成熟先于 Ump1 的降解、复合物的收紧，最后 Pba1-Pba2 的释放。
