Chemistry & BioChem Seminar


Prof. Alexander V. Statsyuk, Host: Liming Zhang
Northwestern University, Dept of Chemistry

Date and Location

Friday December 05, 2014 4:00pm
4606 PSBN


  Chemical Tools to Explore Ubiquitin Signaling
Our research program is focused on the development of chemical tools to study the role
of ubiquitin signaling. Specifically we have developed selective small molecule inhibitors
of the ubiquitin activating E1 enzymes that lead to a complete inhibition of the ubiquitin
system. These inhibitors contain sulfamate moiety that acts as a nucleophile reacting
with the E1~Ub thioester to form ubiquitin adenylate mimic that binds tightly to the E1
enzyme and inhibits its function. During these studies we have uncovered the potential
of N-acylsulfamates as useful pH-cleavable linkers for a variety of applications. We used
those to design a novel class of pH-cleavable photocrosslinkers to study E2/E3
interactions, and discovered the second E2 enzyme binding site on E6-AP ligase.
! Our other research directions included the development of irreversible tethering
technology, a useful technology to discover covalent enzyme and protein-protein
interaction inhibitors. Using this technology we discovered first-in-class inhibitors of
HECT E3 Nedd4-1 enzyme processivity. This types of inhibitors are novel and offer
opportunities to decouple physiological functions of HECT E3 ligases related to their
ability to mono- and polyubiquitinate protein substrates. To visualize the binding mode of
these inhibitors, we obtained the first crystal structure of Nedd4-1 enzyme bound to its
covalent small molecule inhibitor, and subsequently developed more potent inhibitors of
Nedd4-1 enzyme.
! Finally, we will discuss the development of novel fluorescent assays to screen
for inhibitors or activators of HECT E3 ubiquitin ligases. Typical assays for E3 ligases
are very complex and require ATP, Ubiquitin, E1, E2, and E3s which increases the cost
of the assay, and leads to false positive results due to the inhibition of E1 or E2
enzymes. To simplify the assay, we have developed a novel reaction, in which protein
ubiquitination and polyubiquitin chain synthesis are achieved in the absence of ATP, E1
and E2 enzymes, and in the presence of the chemically activated ubiquitin. Finally we
will discuss future directions.

Host:  Liming Zhang