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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.edu

Jun Yin

Georgia State University, USA

Jun Yin, Organic Chem Curr Res 2018, Volume 7

DOI: 10.4172/2161-0401-C3-027