COSAM » COSAM Faculty » Chemistry and Biochemistry » Holly Ellis

Holly Ellis
Chemistry and Biochemistry
William P. Molette Professor

Research Areas: Biochemistry

Office: 359 Chemistry Building

179 Chemistry Building
Auburn, AL 36849

Phone: (334) 844-6991
Fax: (334) 844-6959


Ph.D., Wake Forest University
B.S. University of Central Florida

Professional Employment

Associate Professor, Department of Chemistry and Biochemistry, Auburn University
2007 - present
Program Officer, NSF
2011 - 2012
Assistant Professor, Department of Chemistry and Biochemistry, Auburn University
2001 - 2007
NIH Post-doctoral, Texas A&M University

Honors and Awards

Final Lecturer Nominee
Spring 2014
COSAM Teaching Award
Spring 2010
SGA COSAM Teaching Award
Spring 2010
AED Honorary Membership/Favorite Faculty
Spring 2006
Favorite Faculty Nominee-Panhellenic Council
Fall 2005
COSAM Advisor Award
Spring 2004
Mortar Board Favorite Educator Award
Spring 2003
Inducted as a Golden Key Honorary Member
Spring 2003
Camp War Eagle Faculty Honoree
Spring 2003
National Science Foundation travel award to attend the 12th International Symposium on Flavins and Flavoproteins at the University of Calgary
Summer 1996
Postdoctoral, National Research Service Award (NIH-NIGMS)
1999 - 2001
Graduate Fellowship, Wake Forest University School of Medicine
1993 - 1995

Professional Activities

Editorial Board, BBA-Proteins and Proteomics , 2013-present
Southeast Enzyme Conference Organizer. April 20th, 2013, Atlanta Georgia
Reviewer: Biochemistry, Archives of Biochemistry and Biophysics, JEIMC, JACS, Journal of Biological Chemistry, BBA, NSF
NSF “Expert”, 2012
NSF Rotating Program Officer, 2011
NSF Panel Member: March 2014, October 2010, April 2009, April 2008, April 2007, April 2006

Research and Teaching Interests

Our group is interested in understanding the structural and physical dynamics of enzymes that contribute to their functional properties. Our lab has focused our research efforts on a bacterial two-component system involved in sulfur acquisition, and a mammalian metabolic pathway important in taurine biosynthesis. These catalytically distinct reactions play a vital role in maintaining appropriate sulfur levels in bacterial and mammalian systems.

Alkanesulfonate Monooxygenase System

          For many bacterial organisms, inorganic sulfate is an important metabolite in the biological synthesis of sulfur-containing macromolecules. Inorganic sulfur is poorly represented in aerobic soil therefore bacteria in soil environments must have alternative sources for obtaining this element. When Escherichia coli is deprived of inorganic sulfur or cysteine, a set of sulfate-starvation-induced (Ssi) proteins is produced at increased levels. Two of these proteins include an FMN reductase (SsuE) and an FMNH2-utilizing monooxygenase (SsuD). This alkanesulfonate monooxygenase system is involved in the acquisition of sulfur through the reduction of alkanesulfonates to sulfites and the corresponding aldehyde. The system belongs to a family of two-component enzyme systems that utilize FMN as a substrate rather than a bound prosthetic group. The number of bacterial flavin-dependent monooxygenases that utilize flavin as a substrate has increased significantly with new systems continually being identified. We are interested in the novel mechanism of desulfonation by this system, and identifying how conformational flexibility of these enzymes contributes to their function.

Taurine Biosynthetic Pathway

           The sulfur-containing nonprotein amino acid, taurine, plays an important protective role in a wide variety of mammalian physiological functions. Many of the biological functions of taurine rely on the intracellular concentrations of taurine, which is determined by the cells capacity to synthesize this metabolite. Taurine can be synthesized by several different mechanisms, but is primarily produced by the cysteine dioxygenase pathway. In the initial reaction, cysteine is converted to cysteine sulfinic acid by the enzyme cysteine dioxygenase. The reaction catalyzed by cysteine dioxygenase (CDO) has been shown to be a primary step in the production of taurine. The cysteine sulfinic acid formed can branch to form pyruvate and sulfite by aspartate amino transferase or taurine by cysteine sulfinate decarboxylase (CSD). By catalyzing the first step in the pathway, CDO plays a critical role in the maintenance of cysteine and taurine levels in cells. The focus of our research is to obtain a detailed understanding of the catalytic mechanism of each enzyme in the taurine biosynthetic pathway to determine how this important metabolite is properly maintained in the cell.

Selected Publications

  1. Njeri, C. and Ellis, H.R. (2014) Shifting redox states of the iron center partitions CDO between crosslink formation or cysteine oxidation. Arch. Biochem. Biophys. 558, 61-69. doi:10.1016/
  2. Armacost, K, Musila, J., Gathiaka, S., Ellis, H.R., and Acevedo, O. (2014) Exploring the catalytic mechanism of alkanesulfonate monooxygenase using molecular dynamics. Biochemistry 53, 3308–3317.
  3. Driggers, C. M., Dayal, P., Ellis, H. R. and Karplus, P. A. (2014) Crystal structure of Escherichia coli SsuE: Defining a catalytic cycle for FMN reductases of the flavodoxin-like superfamily. Biochemistry 53, 3509-3519.
  4. Robbins, J. M. and Ellis, H. R. (2014) Steady-state kinetic isotope effects support a complex role of Arg226 in the proposed desulfonation mechanism of alkanesulfonate monooxygenase. Biochemistry 53, 161-168.
  5. Robbins, J. M., and Ellis, H. R. (2012) Identification of critical steps governing the two- component alkanesulfonate monooxygenase catalytic mechanism, Biochemistry 51, 6378- 6387. 

Last updated: 02/13/2017