Post on 19-Dec-2015
A heterodimeric complex that promotes the assembly of mammalian 20S proteasomes
Vol 437|27 October 2005|doi:10.1038/nature04106Yuko Hirano
生科四甲 91390355
葉孟軒
Model for the Structure of the 26S Proteasome
名詞解釋
26S Proteasome : 真核生物體中一種蛋白質水解酶,為 multisubunt ,是由 20S 的核心 proteasome 和兩軸上的 19S regulatory complexs 組合而成,而 20S 是由 28 個 subunits 組成, ” α1-
7β1-7β1-7α1-7” 為其排列成圓筒狀方式 PAC1 & PAC2 : Proteasome assembling chaperone-1 & 2 ,
為此篇論文討論的重點, PAC1 和 PAC2 會形成一個 heterodimers ,能幫助 proteasome precursors 聚集成為成熟的 preteasome
MG132 :
實驗方法
DNA constructs and cell culture. Protein extracts, immunological analysis and antib
odies. Glycerol gradient analysis Purification of PAC1-PAC2 complex Pulse-chase experiments RNAi experiments Assay of proteasome activity Chromatography
density
Introduction “Half-proteasome” 包括一個 α ring + 一個 β ring
+ heterodimeric 還有一個 chaperone Ump1 。要組成一個成熟的 proteasome ,就需要兩個 Half-proteasome dimerize ,在結合之前 β ring 上的 propeptide會先脫離,而且 Ump1( 人體中為 hUmp1) 也會降解離去;在整個 assembling 過程當中, heterodimeric所扮演的角色就是促進 precursor proteasome 構型組成,此外還能提供一個鷹架,協助 α ring 組成,還有保持充足的 α rings 以構成 half-proteasome ,接下來就是要利用實驗的方法去證實 heterodimeric 的這些功能。
圖一
PAC-1 and PAC-2 associate with precursor proteasomes.
4~24%
圖二PAC-1 and PAC-2 associate with precursor proteasomes.
The PAC1–PAC2 heterodimer is rapidly degraded by proteasomes. 圖三
4~17%
The PAC1–PAC2 heterodimer is rapidly degraded by proteasomes. 圖四
圖四siRNA-mediated knockdown of PAC1 and PAC2 impairs proteasome assembly.
4~24%
圖六
PAC1–PAC2 provides a scaffold for a-ring formation.
圖六PAC1–PAC2 provides a scaffold for a-ring formation.