In situ structural studies of tripeptidyl peptidase II (TPPII) reveal spatial association with proteasomes
In situ structural studies of tripeptidyl peptidase II (TPPII) reveal spatial association with proteasomes
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DOI：
10.1073/pnas.1701367114
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发表时间：
2017-04-25
影响因子：
11.1
通讯作者：
Baumeister, Wolfgang
中科院分区：
文献类型：
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作者：
Fukuda, Yoshiyuki;Beck, Florian;Baumeister, Wolfgang
三肽基肽酶II （TPPII）是一种作用于26S蛋白酶体下游的真核蛋白酶；它从蛋白酶体释放的降解产物中去除三肽。体外结构研究揭示了TPPII的基本结构，这是一种两链线性聚合物，可组装形成类似于6mda的纺锤形复合物。依赖于蛋白浓度，TPPII具有明显的多态性倾向。因此，其在体内的结构尚不清楚。为了解决这一问题，我们对大鼠海马神经元的低温电子断层扫描进行了模板匹配，以了解TPPII的发生和空间分布。尽管TPPII的丰度很低，但用Volta相板记录的层析图的质量使TPPII的详细结构分析成为可能。两种不同的组装状态（36米和32米）共存，偶尔也会有更长的链延伸形式。对TPPII和26S蛋白酶体相对位置的距离分析证实了这两种复合物在空间上的关联，这与TPPII在蛋白酶体后降解中的作用一致。
Tripeptidyl peptidase II (TPPII) is a eukaryotic protease acting downstream of the 26S proteasome; it removes tripeptides from the degradation products released by the proteasome. Structural studies in vitro have revealed the basic architecture of TPPII, a two-stranded linear polymer that assembles to form a spindle-shaped complex of similar to 6 MDa. Dependent on protein concentration, TPPII has a distinct tendency for polymorphism. Therefore, its structure in vivo has remained unclear. To resolve this issue, we have scrutinized cryo-electron tomograms of rat hippocampal neurons for the occurrence and spatial distribution of TPPII by template matching. The quality of the tomograms recorded with the Volta phase plate enabled a detailed structural analysis of TPPII despite its low abundance. Two different assembly states (36-mers and 32-mers) coexist as well as occasional extended forms with longer strands. A distance analysis of the relative locations of TPPII and 26S proteasomes confirmed the visual impression that these two complexes spatially associate in agreement with TPPII's role in postproteasomal degradation.