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. Author manuscript; available in PMC: 2020 Jul 8.
Published in final edited form as: Nat Chem. 2019 Jun 10;11(7):644–652. doi: 10.1038/s41557-019-0278-x

Figure 4. Ub4ix cyclic peptide inhibits 26S proteasomal activity in vitro.

Figure 4.

HA-α-globin-K48Ub4 (5 μM) and 26S proteasome (150 nM) were combined in the presence and absence of cyclic peptide Ub4ix, linear-Ub4ix or MG132. Before and after incubation, products were separated on SDS-PAGE gel, electro-blotted and probed with anti-HA antibody. Linear-Ub4ix offers no protection to HA-α-globin-K48Ub4 from the activity of the proteasome, resulting in degradation. Cyclic peptide Ub4ix, at a similar concentration to the HA-α-globin-K48Ub4 substrate (5 μM) can protect it from degradation by the proteasome, a similar result to the adding the direct proteasome inhibitor MG132.