title: Molecular architecture and assembly mechanism of Drosophila tripeptidyl peptidase II.
abstract: In eukaryotes, tripeptidyl peptidase II (TPPII) is a crucial component of the proteolytic cascade acting downstream of the 26S proteasome in the ubiquitin-proteasome pathway. It is an amino peptidase belonging to the subtilase family removing tripeptides from the free N terminus of oligopeptides. The 150-kDa subunits of Drosophila TPPII assemble into a giant proteolytic complex of 6 MDa with a remarkable architecture consisting of two segmented and twisted strands that form a spindle-shaped structure. A refined 3D model has been obtained by cryoelectron microscopy, which reveals details of the molecular architecture and, in conjunction with biochemical data, provides insight into the assembly mechanism. The building blocks of this complex are apparently dimers, within which the 150-kDa monomers are oriented head to head. Stacking of these dimers leads to the formation of twisted single strands, two of which comprise the fully assembled spindle. This spindle also forms when TPPII is heterologously expressed in Escherichia coli, demonstrating that no scaffolding protein is required for complex formation and length determination. Reciprocal interactions of the N-terminal part of subunits from neighboring strands are probably involved in the formation of the native quaternary structure, lending the TPPII spindle a stability higher than that of single strands.
authors: Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, D-82152 Martinsried, Germany. rockel@biochem.mpg.de
authors: Beate
authors: B
authors: Rockel
authors: Jürgen
authors: J
authors: Peters
authors: Shirley A
authors: SA
authors: Müller
authors: Gönül
authors: G
authors: Seyit
authors: Philippe
authors: P
authors: Ringler
authors: Reiner
authors: R
authors: Hegerl
authors: Robert M
authors: RM
authors: Glaeser
authors: Wolfgang
authors: W
authors: Baumeister
mesh_terms: D000626:Aminopeptidases; D000818:Animals; D020285:Cryoelectron Microscopy; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; D004330:Drosophila / Q000201:enzymology*; D019286:Endopeptidase K; D004926:Escherichia coli; D021621:Imaging, Three-Dimensional; D008854:Microscopy, Electron; D008958:Models, Molecular; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D000626:Aminopeptidases; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; C048001:tripeptidyl-peptidase 2; D012697:Serine Endopeptidases; D019286:Endopeptidase K