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College of Natural and Applied Sciences
Rachel Whitaker
Assistant Professor of Biochemistry

Department(s): Chemistry & Physics
Degree(s): PhD
Area of Study: biochemistry
Curriculum Vitae: View Document
   
Email: rwhitaker@coastal.edu
Office: Kenneth E. Swain Hall Room 215
Phone: 843-349-4086
Website: http://www.rwhitakerscience.com
   
Biography:
Dr. Whitaker grew up in Arizona. Her undergraduate education was completed at the University of Arizona and her graduate education was completed at the University of Illinois, U-C. She completed her postdoctoral training with Dr. Scott Silverman at the University of Illinois, U-C.

Dr. Whitaker is married to Daniel Whitaker and they have two children Adelae and Serena.

The Whitaker Lab at Coastal Carolina University researches three main topics:
First, we are interested in utilizing directed evolution approaches to enhance the catalysis, thermalstability and pH tolerance of the laccase enzyme from Trametes versicolor and then to utilize this enzyme as an aquatic bioremediation tool. It has been shown that this laccase enzyme can oxidize natural estrogens,1 nonylphenol,2 bisphenol-A,3 polychlorinated biphenyl compounds (pcb) 4 and many other cyclic anthropogenic pollutants. The success of using laccase to oxidize cyclic anthropogenic pollutants is profound. The significant drawbacks of using laccase in bioremediation efforts have been that first, laccase’s optimal pH is ~5.0, second, expression and purification of laccase in bulk has been difficult, and third, the temperature range of activity and stability of laccase is limited5, 6. Therefore, we hope to improve laccase utility through directed evolution approaches.

Second, we are interested in determining tRNA structural changes upon binding to different cations and characterizing these interactions through stopped-flow kinetic analysis. The tRNA molecule naturally binds to Mg2+, which allows it to assume an “L-shaped” conformation.8 We then asked the question, can tRNA bind to other metals? If so, would binding to different metals impact the tRNA’s three-dimensional shape? Numerous undergraduate research students were excited to begin this work. Since starting this project, undergraduate students have successfully synthesized tRNA through a process called in vitro transcription. In addition, they have begun to bind tRNA to various metals and determine its tertiary structural changes through gel electrophoresis analysis. We are currently in collaboration with the SC NMR facility at Claflin University to gather detailed structural information on tRNAs in complex with metal ions. In addition, we are in collaboration with USC to gather equilibrium rate data for these tRNA-metal complexes.

Lastly, we are interested in biochemically characterizing aminoacyl-tRNA synthetases (aaRSs). Each aaRS binds to their respective amino acid, tRNA and ATP to carry out the aminoacylation reaction. The aminoacylation reaction provides charged tRNA products that can then be utilized by the ribosome machinery to generate polypeptides. Therefore, this family of enzymes are essential for cellular function and as a result are a favorite target by which potential pharmaceuticals can be generated. We are currently biochemically testing various inhibitory compounds for aaRSs and characterizing their interactions. This project is a collaborative effort between the Whitaker and Wakefield labs at CCU.

1. Cardinal-Watkins, C., and Nicell, J. A. (2011) Enzyme-Catalyzed Oxidation of 17beta-Estradiol Using Immobilized Laccase from Trametes versicolor, Enzyme research 2011, 725172.
2. Catapane, M., Nicolucci, C., Menale, C., Mita, L., Rossi, S., Mita, D. G., and Diano, N. (2013) Enzymatic removal of estrogenic activity of nonylphenol and octylphenol aqueous solutions by immobilized laccase from Trametes versicolor, Journal of hazardous materials 248-249, 337-346.
3. Margot, J., Maillard, J., Rossi, L., Barry, D. A., and Holliger, C. (2013) Influence of treatment conditions on the oxidation of micropollutants by Trametes versicolor laccase, New biotechnology.
4. Keum, Y. S., and Li, Q. X. (2004) Fungal laccase-catalyzed degradation of hydroxy polychlorinated biphenyls, Chemosphere 56, 23-30.
5. Madzak, C., Mimmi, M. C., Caminade, E., Brault, A., Baumberger, S., Briozzo, P., Mougin, C., and Jolivalt, C. (2006) Shifting the optimal pH of activity for a laccase from the fungus Trametes versicolor by structure-based mutagenesis, Protein engineering, design & selection : PEDS 19, 77-84.
6. Bohlin, C., Jonsson, L. J., Roth, R., and van Zyl, W. H. (2006) Heterologous expression of Trametes versicolor laccase in Pichia pastoris and Aspergillus niger, Applied biochemistry and biotechnology 129-132, 195-214.
7. Bertrand, T., Jolivalt, C., Briozzo, P., Caminade, E., Joly, N., Madzak, C., and Mougin, C. (2002) Crystal structure of a four-copper laccase complexed with an arylamine: insights into substrate recognition and correlation with kinetics, Biochemistry 41, 7325-7333.
8. Green, R., and Noller, H. F. (1997) Ribosomes and translation, Annu Rev Biochem 66, 679-716.