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Organic Chemistry: Current Research | ISSN: 2161-0401 | Volume 7
July 18-19, 2018 | Atlanta, USA
24
th
Global
Organic & Inorganic Chemistry Conference
Chemical tools to probe protein ubiquitination
U
biquitin (UB) is transferred through an E1-E2-E3 enzymatic cascade to the substrate proteins to regulate their stability
and biological functions in the cell. The human genome encodes 2 E1s, 45 E2s, and more than 600 E3s. Together they
assemble a complex network of UB transfer for the modification of cellular proteins. Currently, key questions are unsolved
on how to identify ubiquitination targets of important E3s to map them on the cell signaling networks, and how UB chains of
specific linkages are assembled to encode unique signals in the cell. We have developed a method that we refer to as “orthogonal
UB transfer” (OUT) to untangle the complexity of protein ubiquitination networks. The key to OUT is to engineer a cascade
of engineered E1, E2 and E3 enzymes (xE1, xE2, and xE3) that exclusively transfers an engineered UB (xUB) to the substrates
of a xE3. We express xUB and the OUT cascade in the cell, purify xUB-conjugated proteins, and reveal their identities by
proteomics. The proteins from the OUT screen are the potential substrates of the E3 in the OUT cascade. We have developed
OUT cascades with HECT E3 E6AP and U-box E3s E4B and CHIP and identified new cellular circuits regulated by these E3s.
To investigate the mechanism of E2-catalyzed UB chain synthesis, we have generated linkage-specific di-UB conjugates by
unnatural amino acid incorporation and expressed protein ligation. The di-UB conjugates mimic the binding modes of donor
and acceptor UBs at the E2 active site for UB chain synthesis. By characterizing the structure of E2-diUB conjugates, we are to
reveal how E2 regulates the synthesis of UB chains of different linkages.
Biography
Jun Yin has completed his PhD from University of California, Berkeley and postdoctoral studies from Harvard Medical School. He is an Associate Professor at the
Department of Chemistry of the Georgia State University. His research focus is ubiquitin-mediate cell signaling processes and the catalytic mechanisms of protein
ubiquitination enzymes.
junyin@gsu.eduJun Yin
Georgia State University, USA
Jun Yin, Organic Chem Curr Res 2018, Volume 7
DOI: 10.4172/2161-0401-C3-027