Interplay between Structure and Charge as audKey to Allosteric Modulation of Human 20SudProteasome by the Basic Fragment of HIV-1udTat Protein

摘要

The proteasome is a giant protease responsible for degradation of themajority of cytosolicudproteins. Competitive inhibitors of the proteasome are used against aggressive blood cancers.udHowever, broadening the use of proteasome-targeting drugs requires new mechanisticudapproaches to the enzyme’s inhibition. In our previous studies we described Tat1 peptide, anudallosteric inhibitor of the proteasome derived from a fragment of the basic domain of HIV-Tat1udprotein. Here, we attempted to dissect the structural determinants of the proteasome inhibitionudby Tat1. Single- and multiple- alanine walking scans were performed. Tat1 analogs with stabilizedudbeta-turn conformation at positions 4–5 and 8–9, pointed out by the molecular dynamicsudmodeling and the alanine scan, were synthesized. Structure of Tat1 analogs were analyzedudby circular dichroism, Fourier transform infrared and nuclear magnetic resonance spectroscopyudstudies, supplemented by molecular dynamics simulations. Biological activity tests andudstructural studies revealed that high flexibility and exposed positive charge are hallmarks ofudTat1 peptide. Interestingly, stabilization of a beta-turn at the 8–9 position was necessary toudsignificantly improve the inhibitory potency.