Research Interests:
We are interested in studying transition metal-containing proteins and protein-based free radicals as well as their medical relevance using a combination of biochemical, bioinformatics, cell biology, structural and spectroscopic tools. The long term goal of our study is to determine the chemical basis for the biological roles and physiological effects of metal ions and protein-based free radicals. Our current research has two major themes: (1) understanding of how metalloenzymes generate biologically important metabolites from amino acids and how the catabolic pathways are regulated and (2) understanding of how metalloproteins participate in cell signaling modulations.
Are 20 amino acids enough? probably suffient for giving structural variety but not enough for all of the chemical needs. There are at least 600 more amino acid-like or amino acid-derived essential compounds known in our life. Two out of the three on-going research projects in our metalloprotein laboratory are dealing with the mechanistic enzymology of amino acid catabolic pathways. The first project concerns tryptophan catabolism which is linked to neuropsychiatric problems. We are engaged in studying mechanistic enzymology and regulation of tryptophan's kynurenine pathway. The chemical mechanism of heme-based tryptophan 2,3-dioxygenase (TDO), zinc-dependent α-amino-β-carboxymuconate-ε-semialdehyde decarboxylase (ACMSD), and NAD-dependent α-aminomuconate semialdehyde (AMS) dehydrogenase of the kynurenine pathway are being elucidated by using biochemical and spectroscopic approaches. Moreover, an unusual diheme enzyme, MauG, is also included in our mechanistic study and spectroscopic work. The diheme enzyme oxidizes protein-bound tryptophan residues on a substrate protein to convert it to an active enzyme.
Our second project is placed on the chemical mechanisms and regulation of sulfur metabolism. We are interested in the endogenous thiol dioxygenases, namely cysteine dioxygenase and cysteamine dioxygenase. These two nonheme Fe enzymes play crucial roles in controlling sulfur homeostasis and contribute to human disease states.
Our third project concerns the molecular mechanism of signal transduction regulation by metalloproteins. We employ a wide array of biochemical, biophysical, bioinformatics, structural, molecular and cellular biology tools to study a nuclear metalloprotein that participates in cell signaling through modulation of the transactivation of inducible transcription factors such as NF-κB.
Through our studies on the above selected systems we hope to learn how the proteins govern the biological function of the transition metal ions and to contribute to the development of new strategies to tackle human diseases.

(Liu Lab current postdoctoral associate and graduate students 2011)
Spotlight - Life is in a sea of metals ions and protein radicals
Unraveling of an over 60-year old mystery of peroxide reactivation mechanism in tryptophan 2,3-dioxygenase: How is the active Fe(II) enzyme generated from Fe(III)-TDO by an oxidant (i.e., hydrogen peroxide)
(J. Biol. Chem., 2011, 286, 26541-26554)
Trapping an unprecedented bis-Fe(IV) species in a di-heme enzyme MauG for a remarkably long-range enzyme catalysis
(Proc. Natl. Acad. Soc. USA, 2008, 105, 8597-8600)
Establishing a new protein subfamily for novel transition metal-mediated O2-independent decarboxylase/hydratase mechanisms
(JACS 2005, 127, 12282-12290; JACS 2007, 129, 9278-9279; Biochemistry, 45, 10407-10411)
Awards & Services
2011 Chair, 40th Southeastern Magnetic Resonance Conference (SEMRC 2011), Atlanta, November 4-6, 2011.
2010 Member (2010-2012), EMR Advisory Committee, The National High Magnetic Field Laboratory
2010- Director of Chemistry Core Facility, Natural Science Center, GSU
2009 NSF Program Review Panelist
2009 Distinguished Cancer Scientist Award, The Georgia Cancer Coalition
2009 Principal Investigator, NSF Grant No. MCB-0843537
2009 Cleon F. Arrington Research Initiation Award, Georgia State University
2008 Visiting Professor at Kansai University, Osaka, Japan
2006 Steering Committee member, Neuroscience Graduate Curriculum, UMMC, Jackson, MS
2006 Ad hoc member of the MSFA Study Section, NIH
2005 NSF CHE & MCB proposal ad hoc reviewer
2003 Ralph E. Powe Junior Faculty Enhancement Award in Life Sciences, The Oak Ridge Associated Universities (ORAU)
2002 Paul D. Boyer Award for Research Excellence, Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota
2002 Cyrus P. and Anne R. Barnum Travel Award, Minnesota Medical Foundation, Minneapolis, MN
1999 Wenner-Gren Center Foundation Travel Fellowship, Stockholm, Sweden
1997 Poster Presentation Award, Society of Chemical Industry (SCI), London, UK
1996 Royal Society K.C. Wong Fellowship, The Royal Society, London, UK
1995 National Prize for Promotion of Science and Technology from National Education Commission, Beijing, China
1993 Principal Investigator, Chinese National Science Foundation Research Grant, Beijing, China
1991 Presidential Award, Chinese Academy of Sciences (CAS), Beijing, China
Invited Faculty Seminars & Talks in Scientific Meetings
01/2013 23rd Enzyme Mechanisms Conference (23rd EMC), Coronado, CA
07/2012 Gordon Research Conferences (GRC) 2012- Protein Cofactors, Radicals and Quinones GRC, South Hadley, MA
07/2012 International Conference on Porphyrins and Phthalocyanines (ICPP-7), Jeju, Korea
10/2011 Florida Institute of Technology (seminar)
09/2011 University of Wisconsin-Milwaukee (colloquium)
08/2011 15th International Conference on Biological Inorganic Chemistry, Vancouver, Canada
07/2011 53rd Rocky Mountain Conference - EPR Symposium, Snowmass, CO
06/2011 The 2011 Georgia Cancer Summit, Macon, GA
10/2010 39th Southeastern Magnetic Resonance Conference (39th SEMRC), Florida
09/2010 Albert Einstein College of Medicine of Yeshiva University (seminar)
12/2009 Emory University (colloquium)
11/2009 Georgia Institute of Technology (seminar)
09/2009 University of Florida (seminar)
07/2009 14th International Conference on Biological Inorganic Chemistry, Nagoya, Japan
08/2008 Auburn University (seminar)
06/2008 Osaka University (seminar)
05/2008 Tohoku University (seminar)
05/2008 Kansai University (seminar)
04/2008 The 235th National American Chemical Society Conference, New Orleans, LA
03/2008 University of Southern Mississippi (seminar)
01/2008 Gordon Research Conferences (GRC) 2008 - Protein Cofactors, Radicals, and Quinones, Ventura, CA
10/2007 Pennsylvania State University (seminar)
01/2006 Gordon Research Conferences (GRC) 2006- Metals in Biology, Ventura, CA
01/2006 The Inaugural Texas Enzyme Mechanism Conference, Austin, TX
07/2003 Gordon Research Conferences (GRC) 2003 - Enzyme, Coenzyme & Metabolic Pathways (Poster talk)
06/2003 Jackson State University - NIH-Sponsored SCORE Seminar Series
02/2003 Mississippi State University (seminar)
Recent Selected Peer-Reviewed Research Articles (for a complete list, click here)
Interested in joining our metalloprotein research laboratory?
Georgia State is a major research university in the southeast region of the United States. Atlanta, where our laboratory is located, is a rising metropolis that is fun to live, with year-long comfortable weather and numerous international supermarkets scattered throughout neighborhoods in the city. As the main hub and headquarters of Delta Airlines, it is easy to get around to anywhere in the world. Our lab is well-equipped with biochemical and spectroscopic instrumentation (click here for a virtual lab tour). We currently have openings for a post-doctoral associate as well as graduate students. Contact Dr. Liu by email (Feradical at gsu.edu) if interested.

(The major tryptophan catabolic pathways are shown on the above banner)