A giant protease with a twist: the TPP II complex from Drosophila studied by electron microscopy

摘要: Tripeptidyl peptidase II (TPP II) is an exopeptidase of the subtilisin type serine proteases that thought to act downstream proteasome in ubiquitin-proteasome pathway. Recently, a key role pathway parallel has been ascribed TPP II, which forms giant protease complex mammalian cells. Here, we report 900-fold purification from Drosophila eggs and demonstrate via cryo-electron microscopy melanogaster also complex. The presented three-dimensional reconstruction 57 x 27 nm at 3.3 resolution reveals 150 kDa subunits form superstructure composed two segmented twisted strands. Each strand 12.5 width 11 segments enclose central channel.