Proteasome Endopeptidase ComplexProteasome InhibitorsMultienzyme ComplexesCysteine EndopeptidasesCysteine Proteinase InhibitorsLeupeptinsUbiquitinsPeptide HydrolasesProtein SubunitsAcetylcysteineUbiquitinSaccharomyces cerevisiaeMass SpectrometryProteinsMolecular Sequence DataBoronic AcidsAmino Acid SequenceProtein BindingPyrazinesProtease InhibitorsUbiquitinationProteolysisPolyubiquitinUbiquitin-Protein LigasesUbiquitinated ProteinsOligopeptidesThermoplasmaApoptosisCell Line, TumorCell LineChymotrypsinProtein Processing, Post-TranslationalEndopeptidasesAdenosine TriphosphatasesLactonesSaccharomyces cerevisiae ProteinsBlotting, WesternEndoplasmic Reticulum