Hybrid molecular structure of the giant protease tripeptidyl peptidase II.
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.
Chuang
Crystal K
CK
Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA.
Rockel
Beate
B
Seyit
Gönül
G
Walian
Peter J
PJ
Schönegge
Anne-Marie
AM
Peters
Jürgen
J
Zwart
Petrus H
PH
Baumeister
Wolfgang
W
Jap
Bing K
BK
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
D020035:Holoenzymes; D000626:Aminopeptidases; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; C048001:tripeptidyl-peptidase 2; D012697:Serine Endopeptidases; D020860:Subtilisin