James Hougland

Associate Professor, Chemistry

Research Interests

Bioorganic chemistry, biochemistry, enzymology, post-translational modification, molecular biology

Professor Hougland's full CV can be found here.


  • B.A., 1998, Northwestern University
  • Ph.D., 2005, University of Chicago
  • Postdoctoral Fellow, 2005-2010, University of Michigan 

Honors & Awards:

  • American Diabetes Association Junior Faculty Development Award, 2016-2018
  • Lewis H. Sarrett Undergraduate Research Award, 1998
  • McCormick Graduate Fellowship, 1998-1999
  • National Institutes of Health Postdoctoral Fellowship, 2006-2009
  • March of Dimes Basil O'Connor Starter Scholar Research Award, 2014-2016


  • CHE 275: Organic Chemistry I
  • CHE 600: Chemistry and Biology of Posttranslational Modification
  • CHE 675: Advanced Organic Chemistry
  • CHE 685: Organic Mechanisms

Research Interests: Protein Post-translational Modification

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Research in my group focuses on the chemistry and biology of protein post-translational modification. Post-translational modifications play an essential role in regulating protein function, with these modifications linked to multiple human diseases such as cancer, cardiovascular disease, and obesity. The enzymes responsible for these chemical transformations face a daunting molecular recognition challenge, needing to efficiently identify and act upon their pool of substrates within a complex mixture of other proteins within the cell. Understanding the strategies employed by these enzymes will help identify novel substrates, while potentially illuminating new targets for therapeutic intervention and inhibitor development. Drawing from chemistry, biochemistry, and molecular biology, my research program investigates enzymes involved in post-translational modification with the long term goal of defining how these enzymes and the modifications they perform control biological activity by altering protein structure, function, and localization. We focus on enzymes involved in protein lipidation pathways, such as prenyltransferases, proteases, and acyltransferases. These enzymes alter protein hydrophobicity through covalent modification, leading to changes in protein localization and activity. Our research examines how these enzymes recognize their substrates and catalyze reactions and the impact of the resulting modification(s) on protein function within the cell.

Research projects

1.  Investigation of ghrelin acylation by ghrelin O-acyltransferase

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Enzymes in the membrane-bound O-acyltransferase (MBOAT) family modify multiple secreted signaling proteins, such as ghrelin, Hedgehog, and Wnt.  Discovery of ghrelin and its stimulating effect on appetite suggests that ghrelin-influenced pathways may provide an avenue for treatment of obesity, with recent studies also linking ghrelin signaling to diabetes.  Ghrelin undergoes a unique serine O-octanoylation modification that appears essential for binding to its cognate receptor.  Ghrelin O-acyltransferase (GOAT), the enzyme that catalyzes this modification, has recently been identified and its biochemical activity confirmed in both mice and humans.  Our goal is to characterize the catalytic mechanism and substrate specificity of GOAT, with these studies providing valuable information for development of GOAT inhibitors and identification of other potential GOAT substrates.

2.  Probing the reactivity threshold for in vivo protein prenylation

Prenylation and subsequent processing steps aid in protein localization to cellular membranes, but a quantitative understanding of this modification pathway remains to be developed.  Furthermore, while many peptide sequences have been shown to be substrates for FTase in in vitro assays, it is unclear how many of these sequences can successfully compete for prenylation by FTase within the pool of potential FTase substrate proteins in the cell.  To address this uncertainty, we aim to determine the minimal substrate reactivity required for a target protein to be recognized and prenylated within a living mammalian cell.  Using a series of reporter proteins whose reactivity with FTase scales over several orders of magnitude, we are developing a calibrated sensor for probing endogenous FTase activity.  Our methodology also provides a novel approach to detect changes in FTase activity within an intact cell in response to genomic mutations or environmental stimuli.  Quantitative determination of the “threshold” for prenylation within the cell will help define the extent of the prenylated proteome and aid in studying prenylation-dependent pathways.

3.  Developing novel prenyltransferase variants with altered substrate selectivity

The prenyltransferases FTase and GGTase-I are examples of multispecific enzymes which must each modify a large number of protein substrates.  The requirement to react with multiple substrates while maintaining selectivity against non-substrates presents a formidable molecular recognition challenge, one requiring both flexibility and fidelity. The first step towards understanding how FTase and GGTase-I accomplish this task is to identify the interactions involved in recognizing protein substrates, and to then define the contribution of each interaction to binding and catalysis. To identity the amino acids used by FTase and GGTase-I to recognize substrates, we are using targeted mutations within the active sites of these enzymes to develop novel enzyme variants with non-natural substrate selectivity. We have found that both FTase and GGTase-I are highly “tunable”, with a small number of mutations leading to drastic changes in enzyme selectivity.  These reengineered prenyltransferases provide insight into how FTase and GGTase-I achieve substrate multispecificity, aiding in the identification of new protein substrates for these enzymes.  The variants we develop also provide new tools for studying the effects of protein prenylation within the cell, allowing us to build a bioengineered prenylation pathway running in parallel to the natural pathway that acts upon only a single target protein. Engineered prenyltransferase variants provide a new avenue for probing the selectivity of prenylation pathway enzymes, determining the effects of prenylation pathway modifications on the cellular function of a protein, and potentially expand the scope of protein prenylation for studies of protein structure and function.

Selected Publications

Darling, J.E.; Zhao, F.; Loftus, R. J.; Patton, L. M.; Gibbs, R. A. and J.L. Hougland. Structure-activity analysis of human ghrelin O-acyltransferase reveals chemical determinants of ghrelin selectivity and acyl group recognition. Biochemistry, 2015, 54, 1100-10

Flynn, S. C.; Lindgren, D. E. and J. L. Hougland. Quantitative determination of cellular farnesyltransferase activity: Towards defining the minimum substrate reactivity for biologically relevant protein farnesylation. ChemBioChem, 2014, 15, 2205-10

Gangopadhyay, S. A.; Losito, E. L. and Hougland, J. L. Targeted reengineering of protein geranylgeranyltransferase type I selectivity functionally implicates active site residues in protein substrate recognition. Biochemistry, 2014, 53, 434-46

Darling, J. E.; Prybolsky, E. P.; Sieburg, M. and Hougland, J. L. A fluorescent peptide substrate facilitates investigation of ghrelin recognition and acylation by ghrelin O-acyltransferase. Anal. Biochem., 2013, 437, 68-76

Hougland, J. L.; Gangopadhyay, S. A. and Fierke, C. A. Expansion of protein farnesyltransferase specificity using “tunable” active site interactions: Development of bioengineered prenylation pathways. J. Biol. Chem., 2012, 287, 38090-100

Hougland, J. L.; Hicks, K. A.; Hartman, H. L.; Kelly, R. A.; Watt, T. J. and Fierke, C. A. Identification of Novel Peptide Substrates for Protein Farnesyltransferase Reveals Two Substrate Classes With Distinct Sequence Selectivities. J. Mol. Biol., 2010, 395, 176-190

Hougland, J. L.; Hicks, K. A.; Hartman, H. L.; Kelly, R. A.; Watt, T. J.; Fierke, C. A. Identification of Novel Peptide Substrates for Protein Farnesyltransferase Reveals Two Substrate Classes with Distinct Sequence Selectivities. J. Mol. Biol., 2010, 395, 176-190.

Hougland, J. L.; Lamphear, C. L.; Scott, S. A.; Gibbs, R. A. and Fierke, C. A. Context-dependent substrate recognition by protein farnesyltransferase. Biochemistry, 2009, 48, 1691-1701