Intermediates in the formation of mouse 20S proteasomes: Implications for the assembly of precursor beta subunits
Intermediates in the formation of mouse 20S proteasomes: Implications for the assembly of precursor beta subunits
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DOI：
10.1093/emboj/16.17.5363
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发表时间：
1997-09-01
期刊：
影响因子：
11.4
通讯作者：
Monaco, JJ
中科院分区：
文献类型：
--
作者：
Nandi, D;Woodward, E;Monaco, JJ
单个蛋白酶体亚基组装成催化活性的哺乳动物20S蛋白酶体的机制尚不清楚，我们使用亚基特异性抗体表征了前体和成熟的蛋白酶体复合体，抗PSMA4(C9)的抗体由α、前体β和加工的β亚基组成，然而，抗PSMA3(C8)和PSMBB(LMP2)的抗体由α和前体β组成，但没有加工的β亚基。这些配合物的半衰期很短，酶活性不强，分子量约为300 kDa。因此，这些结构代表前体蛋白酶体，可能由两个环组成：一个含有亚基，另一个含有前体β亚基。前体蛋白酶体的组装至少经历了两个阶段，前体β亚基PSMB7(Z)、PSMB9(LMP2)和PSMB10(LMP10)先于其他亚基[PSMB1(C5)、PSMB6(Delta)和PSMB8(LMP7)]整合，蛋白酶体的成熟(β亚基的加工和两个β环的并置)伴随着(外部)a环的构象变化，可能是低效的，最后，干扰素-γ对前体或成熟蛋白酶体的半衰期或总量没有显著影响。
The assembly of individual proteasome subunits into catalytically active mammalian 20S proteasomes is not well understood, Using subunit-specific antibodies, we characterized both precursor and mature proteasome complexes, Antibodies to PSMA4 (C9) immunoprecipitated complexes composed of alpha, precursor beta and processed beta subunits, However, antibodies to PSMA3 (C8) and PSMBB (LMP2) immunoprecipitated complexes made up of alpha and precursor beta but no processed beta subunits. These complexes possess short half-lives, are enzymatically inactive and their molecular weight is similar to 300 kDa. Radioactivity chases from these complexes into mature, long-lived similar to 700 kDa proteasomes, Therefore, these structures represent precursor proteasomes and are probably made up of two rings: one containing a subunits and the other, precursor beta subunits, The assembly of precursor proteasomes occurs in at least two stages, with precursor beta subunits PSMB2 (C7-I), PSMB3 (C10-II), PSMB7 (Z), PSMB9 (LMP2) and PSMB10 (LMP10) being incorporated before others [PSMB1 (C5), PSMB6 (delta), and PSMB8 (LMP7)], Proteasome maturation (processing of the beta subunits and juxtaposition of the two beta rings) is accompanied by conformational changes in the (outer) a rings, and may be inefficient, Finally, interferon-gamma had no significant effect on the half-lives or total amounts of precursor or mature proteasomes.