Figure 1.

A schematic showing the preparation of synaptosomal and cytosolic extracts from rat cortices. We include an additional centrifugation step (1 h, 100,000 × g) after solubilization of synaptosomes with NP-40 and before incubation with the UBL-domain. Solubilization leads to binding of an unrelated clathrin complex to the UBL matrix, which complicates the mass spectrometric analysis (data not shown). The respective centrifugation step removes the bulk of this clathrin complex while the proteasome remains fully soluble.