title: Hybrid molecular structure of the giant protease tripeptidyl peptidase II.
abstract: Tripeptidyl peptidase II (TPP II) is the largest known eukaryotic protease (6 MDa). It is believed to act downstream of the 26S proteasome, cleaving tripeptides from the N termini of longer peptides, and it is implicated in numerous cellular processes. Here we report the structure of Drosophila TPP II determined by a hybrid approach. We solved the structure of the dimer by X-ray crystallography and docked it into the three-dimensional map of the holocomplex, which we obtained by single-particle cryo-electron microscopy. The resulting structure reveals the compartmentalization of the active sites inside a system of chambers and suggests the existence of a molecular ruler determining the size of the cleavage products. Furthermore, the structure suggests a model for activation of TPP II involving the relocation of a flexible loop and a repositioning of the active-site serine, coupling it to holocomplex assembly and active-site sequestration.
authors.affiliation: Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA.
authors.forename: Crystal K
authors.initials: CK
authors.lastname: Chuang
authors.forename: Beate
authors.initials: B
authors.lastname: Rockel
authors.forename: Gönül
authors.initials: G
authors.lastname: Seyit
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Walian
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Schönegge
authors.forename: Jürgen
authors.initials: J
authors.lastname: Peters
authors.forename: Petrus H
authors.initials: PH
authors.lastname: Zwart
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Baumeister
authors.forename: Bing K
authors.initials: BK
authors.lastname: Jap
mesh_terms: D000626:Aminopeptidases / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D000818:Animals; D020134:Catalytic Domain; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D004331:Drosophila melanogaster / Q000201:enzymology*; D004789:Enzyme Activation; D020035:Holoenzymes / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D055672:Static Electricity; D013379:Substrate Specificity; D020860:Subtilisin / Q000737:chemistry
chemical_list: D020035:Holoenzymes; D000626:Aminopeptidases; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; C048001:tripeptidyl-peptidase 2; D012697:Serine Endopeptidases; D020860:Subtilisin