College of Arts & Sciences

Aimin Liu

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 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)

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)  

1. Li T, Walker AL, Iwaki H, Hasegawa Y, Liu A (2005) Kinetic and spectroscopic characterization of ACMSD from Pseudomonas fluorescens reveals a pentacoordinate mononuclear metallocofactor.  J. Am. Chem. Soc., 127(35), 12282-12290.    [Abstract]   [PDF]
2. Colabroy KL, Zhai H, Li T, Ge Y, Zhang Y, Liu A, Ealick SE, McLafferty FW, and Begley TP (2005) The mechanism of inactivation of 3-hydroxyanthranilate-3,4-dioxygenase by 4-chloro-3-hydroxyanthranilate. Biochemistry, 44(21), 7623-7631.    [Abstract]    [PDF]
3. Li T, Iwaki H, Fu R, Hasegawa Y, Zhang H, and Liu A (2006) α-Amino-β-carboxymuconic-ε-semialdehyde decarboxylase (ACMSD) is a new member of the amidohydrolase superfamily. Biochemistry, 45(21), 6628-6634.    [Abstract]    [PDF]
4. Martynowski D, Eyobo Y, Li T, Yang K, Liu A, and Zhang H (2006) Crystallographic analysis of α-Amino-β-carboxymuconic-ε-semialdehyde decarboxylase (ACMSD): Insight into the active site and catalytic mechanism of a novel decarboxylation reaction. Biochemistry, 45(35), 10412-10421.   [Abstract]   [PDF]
5. Liu A and Zhang H (2006) Transition metal-catalyzed nonoxidative decarboxylation reactions. Biochemistry (New Concepts article), 45(35), 10407-10411.     [Abstract]    [PDF]
6. Li T, Ma J, Hosler JP, Davidson VL and Liu A (2007) Detection of transient intermediates in the metal-dependent non-oxidative decarboxylation catalyzed by α-amino-β-carboxymuconate-ε-semialdehyde decarboxylase.  J. Am. Chem. Soc., 129(30), 9278-9279.    [Abstract]     [PDF]
7. Yan F, Moon S-J, Liu P, Zhao Z, Lipscomb JD, Liu A, and Liu H-w (2007) Determination of the substrate binding mode to the active site iron of (S)-2-hydroxypropylphosphonic acid epoxidase using ¹⁷O-enriched substrates and substrate analogues. Biochemistry, 46(44), 12628-12638.    [Abstract]     [PDF]
8. Liu A, Li T, and Fu R (2007) Amidohydrolase Superfamily. In: Encyclopedia of Life Sciences. John Wiley & Sons, Ltd: Chichester http://www.els.net/ [DOI: 10.1002/9780470015902.a0020546]  (invited review article).    [Abstract]    [PDF]
9. Li X, Fu R, Liu A, and Davidson VL (2008) Kinetic and physical evidence that the di-heme enzyme MauG tightly binds to a biosynthetic precursor of methylamine dehydrogenase with incompletely formed tryptophan tryptophylquinone. Biochemistry, 47(9), 2908-2912.    [Abstract]     [PDF]
10. Munos JW, Moon S-J, Mansoorabadi SO, Hong L, Yan F, Liu A, and Liu H-w (2008) Purification and characterization of the epoxidase catalyzing the formation of fosfomycin from Pseudomonas syringae. Biochemistry, 47(33), 8726-8735. [Abstract]     [PDF]
11. Li X, Fu R, Lee S, Krebs C, Davidson VL, and Liu A (2008) A catalytic di-heme bis-Fe(IV) form of MauG, Alternative to an Fe(IV)=O porphyrin radical. Proc. Natl. Acad. Sci. U.S.A., 105(25), 8597-8600.    [Abstract]     [PDF]
12. Liu A (2009) Electron Paramagnetic Resonance (EPR) in Enzymology. In: Wiley Encyclopedia of Chemical Biology, John Wiley & Sons, Inc. (invited review article), 1, 591-601.  [Abstract]   [PDF]
13. Huang Y, Zhou Y, Wong HC, Chen Y, Wang S, Castiblanco A, Liu A, Yang JJ (2009) A single EF-hand isolated from STIM1 forms dimer in the absence and presence of Ca²⁺, FEBS J., 276(19), 5589-5597.     [Abstract]     [PDF]
14. Choi M, Sukumar N, Liu A, and Davidson VL (2009) Defining the role of the axial ligand of the type 1 copper site in amicyanin by replacement of methionine with leucine, Biochemistry, 48(39), 9174-9184.     [Abstract]     [PDF]
15. Fu R, Liu F, Davidson VL, and Liu A (2009) Heme iron nitrosyl complex of MauG reveals an efficient redox equilibrium between hemes with only one heme exclusively binding exogenous ligands. Biochemistry, 48(49), 11603-11605.     [Abstract]    [PDF]
16. Thompson AK, Smith D, Gray J, Carr HS, Liu A, Winge DR, and Hosler JP (2010) Mutagenic analysis of Cox11 of Rhodobacter sphaeroides: insights into the assembly of Cu_B of cytochrome c oxidase. Biochemistry, 49(27), 5651-5661. [Abstract]   [PDF]
17. Gupta R, Fu R, Liu A, and Hendrich M (2010) EPR and Mössbauer spectroscopy show inequivalent hemes in tryptophan dioxygenase. J. Am. Chem. Soc., 132(3), 1098-1109.    [Abstract]     [PDF]
18. Choi M, Sukumar N, Mathews FS, Liu A, and Davidson VL (2011) Proline 96 of the copper ligand loop of amicyanin regulates electron transfer from methylamine dehydrogenase by positioning other residues at the protein-protein interface Biochemistry, 50(7), 1265-1273. [Abstract]   [PDF]
19. Shin S, Feng M, Chen Y, Jensen LM, Tachikawa H, Wilmot CM, Liu A, and Davidson VL (2011) The tightly bound calcium of MauG is required for tryptophan tryptophylquinone cofactor biosynthesis. Biochemistry, 50(1), 144-150. [Abstract]   [PDF]
20. Fu R, Gupta R, Geng J, Dornevil K, Wang S, Zhang Y, Hendrich MP, and Liu A (2011) Enzyme reactivation by hydrogen peroxide in heme-based tryptophan dioxygenase. J. Biol. Chem., 286(30), 26541-26554. [Abstract]   [PDF]
21. Tarboush NA, Jensen LMR, Yukl ET, Geng J, Liu A, Wilmot CM, and Davidson VL (2011) Mutagenesis of tryptophan199 suggests that electron hopping is required for MauG-dependent tryptophan tryptophylquinone biosynthesis. Proc. Natl. Acad. Sci. U.S.A., 108(41), 16956-16961. [Abstract]   [PDF]

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.