Molecular mechanism of protein degradation by Tripeptidyl Peptidase II (TPPII)

• Applicant: Dr. Beate Rockel
• Subject Area: Structural Biology
• Term: from 2007 to 2010
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 50417747

Tripeptidyl peptidase II (TPPII) is an exceptionally large protease complex that acts downstream of the 26S proteasome in cytosolic protein degradation. Furthermore, it is involved in antigenic peptide processing, in the degradation of neuropeptides, and plays a crucial role in muscle sepsis and cancer. Drosophila TPPII is a homo-40-mer of 150 kDa subunits, which are assembled into a large spindle-shaped complex. This large size of TPPII is not a prerequisite for its tripeptide-cleaving activity, since the functional homologue Thimet oligopeptidase is only 80 kDa in size. The spindle structure of TPPII ensures high activity at high stability. According to our working hypothesis the spindle is also the structural basis for other functions like selfcompartmentalisation and protein-protein interactions. In order to elucidate the molecular mechanism of TPPII we want to (i) solve the structure of TPPII by cryoelectron microscopy and crystallography, (ii) visualise substrates within TPPII by differential single particle electron microscopy, (iii) localise and visualise TPPII within cells by immunoelectron microscopy, fluorescent microscopy and electron tomography, (iv) identify interacting proteins by weak interaction chromatography and cross-linking.

• DFG Programme: Research Grants