Label-Free Quantitative Proteomics Reveals the Dynamics of Proteasome Complexes Composition and Stoichiometry in a Wide Range of Human Cell Lines

The
proteasome is the main proteolytic system involved in intracellular
proteins homeostasis in eukaryotes. Although the structure of proteasome
complexes has been well characterized, the distribution of its activators
and associated proteins are less studied. Here, we determine the composition
and the stoichiometry of proteasome complexes and their associated
proteins in a wide range of human cell lines using a one-step affinity
purification method and a label-free quantitative proteomic approach.
We show that proteasome complexes are highly dynamic protein assemblies,
the activity of which being regulated at different levels by variations
in the stoichiometry of bound regulators, in the composition of catalytic
subunits and associated proteins, and in the rate of the 20S catalytic
core complex assembly.