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Kayunta Johnson-Winters

Kayunta Johnson-Winters

Associate Professor

Office: 128 Science & Engineering Innovation & Research Building (SEIR) 
Phone: 817 272 3802
Mentis Profile


B.A. Alverno College, 1999
Ph.D. University of Wisconsin-Milwaukee, 2006
Post Doctorate: University of Arizona, 2006-2010 (John H. Enemark)

Enzymes that use Cofactor F420 -- Structure determination by spectroscopic techniques and X-ray crystallography -- Enzyme kinetics and mechanism by rapid-mixing pre-steady state and steady state methods. -- Investigation of reaction intermediates by kinetic isotope effects.


Kayunta Johnson- Winters was born in Bastrop, Louisiana, but grew up in Milwaukee, WI. In 1999, Kayunta received her bachelor’s degree from Alverno College, double majoring in Biology and Chemistry. She received her PhD in Biochemistry, under the academic advisory of Prof. Graham R. Moran at the University of Wisconsin-Milwaukee in 2006. At UWM, her studies were on the structure and kinetics of non-heme iron dioxygenases, primarily, the enzyme, 4-Hydroxyphenylpyruvate Dioxygenase (HPPD). She did her postdoctoral studies at the University of Arizona with Regents Professor, Dr. John H. Enemark. There her project was, "Kinetics and Spectroscopy of Sulfite Oxidase and Related Molybdenum Enzymes." At the University of Arizona, she was awarded the national NIH (National Institutes of Health) fellowship, The Ruth L. Kirschstein Service Award. Her current research interests are to characterize F420 Cofactor Dependent Enzymes.

Mercy A. Oyugi, Ghader Bashiri, Edward N. Baker, and Kayunta Johnson-Winters, Biochem. Biophyica Acta-Proteins and Proteomics, “ Mechanistic Insights into F420-Dependent Glucose-6-Phosphate Dehydrogenase using Isotope Effects and Substrate Inhibition Studies,” (2018) 1866 (2) 387-95.

Cuong Quang Le, Mercy Oyugi, Ebenezer Joseph, Toan Nguyen, Hasmat Ullah, Joshua Aubert, Thein Phan, Joseph Tran and Kayunta Johnson-Winters, Biochemistry and Biophysics Reports, “Effects of Isoleucine 135 side chain length on the cofactor donor-acceptor distance within F420H2:NADP+ Oxidoreductase: A kinetic analysis,” (2017) 9, 114-120

Mercy A. Oyugi, Ghader Bashiri, Edward N. Baker, and Kayunta Johnson-Winters, Biochemistry, “Investigating the reaction mechanism of F420-dependent glucose-6-phosphate dehydrogenase from Mycobacterium tuberculosis: kinetic analysis of the wild-type and mutant enzymes,” (2016) 55, 5566-5577

Ebenezer Joseph, Cuong Quang Le, Toan Nguyen, Mohammad Shawkat Hossain, Frank W. Foss and Kayunta Johnson-Winters, Biochemistry, Evidence of negative cooperativity and half-site reactivity within an F420-dependent enzyme: Kinetic analysis of F420H2:NADP+ oxidoreductase (2016) 55, 1082-90

Cuong Le, Ebenezer Joseph, Toan Nguyen, and Kayunta Johnson-Winters, Protein J, “Expression and Purification of F420:NADP+ Oxidoreductase” (2015), 34, 391-97

M. S. Hossain, C. Q. Le, K. Johnson-Winters and F.W. Foss Jr., Organic and Biomolecular Chemistry, Convenient synthesis of F0 and activity in F420-dependent NADP reductase, (2015), 13, 5082-5

Davis, A.C., Johnson-Winters. K.; Arnold A.R.; Tollin, G.; Enemark J.H.;“Kinetic results for mutations of conserved residues H304 and R309 of human sulfite oxidase point to mechanistic complexities” Metallomics. 2014 6(9):1664-70.

Johnson-Winters, K.; Davis, A.C.; Arnold, A.R.; Berry, R.E.; Tollin, G; Enemark, J.H.;“Probing the role of a conserved salt bridge in the intramolecular electron transfer kinetics of human sulfite oxidase” J Biol Inorg Chem. 2013 (6):645-53.

Astashkin, A.V.; Rajapakshe, A.; Cornelison, M.J.; Johnson-Winters, K., Enemark J.H.;“Determination of the distance between the Mo(V) and Fe(III) heme centers of wild type human sulfite oxidase by pulsed EPR spectroscopy”J Phys Chem B. 2012 116(6):1942-50.

Klein, E.L.; Raitsimring, A.M.; Astashkin, A.V.; Rajapakshe, A.; Johnson-Winters, K.; Arnold, A.R.; Potapov, A.; Goldfarb, D.; Enemark, J.H.;“Identity of the exchangeable sulfur-containing ligand at the Mo(V) center of R160Q human sulfite oxidase” Inorg Chem. 2012 51(3):1408-18.

Johnson-Winters, K.; Nordstrom, A.R.; Davis, A.C.; Tollin, G.; Enemark, J.H.;“Effects of large-scale amino acid substitution in the polypeptide tether connecting the heme and molybdenum domains on catalysis in human sulfite oxidase” Metallomics 2010 Nov;2(11):766-70.

Johnson-Winters, K.; Tollin, G.; Enemark, J.H.;“Elucidating the catalytic mechanism of sulfite oxidizing enzymes using structural, spectroscopic, and kinetic analyses” Biochemistry 2010 49(34):7242-54.

Rajapakshe A.; Johnson-Winters, K.; Nordstrom, A.R.; Meyers, K.T.; Emesh, S.; Astashkin, A.V.; Enemark, J.H.;“Characterization of chloride-depleted human sulfite oxidase by electron paramagnetic resonance spectroscopy: experimental evidence for the role of anions in product release”  Biochemistry 2010 49, 5154-9.

Trevor D. Rapson, Andrei V. Astashkin, Kayunta Johnson-Winters, ,Paul V. Bernhardt, Ulrike Kappler,   Arnold M. Raitsimring, John H. Enemark, “Pulsed EPR investigations of the Mo(V) centers of the R55Q and R55M variants of sulfite dehydrogenase from Starkeya novella” J Biol Chem. 2010 15, 505-514

Kayunta Johnson-Winters, Anna Nordstrom, Safia Emesh, Andrei Astashkine, Asha Rajapakshe, Robert Berry, John Yang, Gordon Tollin, K.V. Rajagopolan and John H. Enemark ”Effects of Interdomain-Tether Length and Flexibility on the Kinetics of Intramolecular Electron Transfer in Human Sulfite Oxidase” Biochemistry 2010 49, 1290-6

Andrei V. Astashkin, Eric L. Klein, Dmitry Ganyushin, Kayunta Johnson-Winters, Frank Neese , Ulrike Kappler, John H. Enemark, “Exchangeable oxygens in the vicinity of molybdenum center of the high-pH form of sulfite oxidase and sulfite dehydrogenase,”Phys Chem Chem Phys. 2009 11, 6733–6742.

Eric L. Klein, Andrei V. Astashkin, Dmitry Ganyushin, Christoph Riplinger, Kayunta Johnson-Winters, Frank Neese, John H. Enemark, “Direct detection and characterization of chloride in the active site of the low-pH form of sulfite oxidase using electron spin echo envelope modulation spectroscopy, isotopic labeling, and density functional theory calculations,” Inorg Chem 2009 48, 4743-52.

Susan Bailey, Trevor Rapson, Kayunta Johnson-Winters, Andrei V. Astashkin and John H. Enemark, “Molecular Basis for Enzymatic Sulfite Oxidation-How Three Conserved Active Site Residues Shape Enzyme Activity” J Biol Chem. 2008 284, 2053-63.

Andrei V. Astashkin, Kayunta Johnson-Winters, Eric L. Klein, Changjian Feng, Heather L. Wilson, K. V. Rajagopalan, Arnold M. Raitsimring, John H. Enemark, “Structural studies of the molybdenum center of the pathogenic R160Q mutant of human sulfite oxidase by pulsed EPR spectroscopy and 17O and 33S labeling “ J Am Chem Soc. 2008 130, 8471-80.

Andrei V. Astashkin, Kayunta Johnson-Winters, Eric L. Klein, Robert S. Byrne, Russ Hille, Arnold M. Raitsimring, John H. Enemark,“Direct demonstration of the presence of coordinated sulfate in the reaction pathway of Arabidopsis thaliana sulfite oxidase using 33S labeling and ESEEM spectroscopy” J Am Chem Soc. 2007 129, I14800-10.

Kayunta Johnson-Winters, Vincent M. Purpero, Michael Kavana, and Graham R. Moran, "The Accumulation of Mulitple Intermediates in the Catalytic Cycle of (4-Hydroxyphenyl)pyruvate Dioxygenase from Streptomyces avermitilis." Biochemistry 2005 44, 7189-7199.

June M. Brownlee, Kayunta Johnson-Winters, David H.T. Harrison, and Graham R. Moran, "Structure of the Ferrous Form of (4-Hydroxyphenyl)pyruvate Dioxygenase from Streptomyces avermitilis in Complex with the Therapeutic Herbicide, NTBC” Biochemistry 2004 43, 6370-6377.

Kayunta Johnson-Winters, Vincent M. Purpero, Michael L. Kavana, Tamara N. Nelson, and Graham R. Moran "(4-Hydroxyphenyl)pyruvate Dioxygenase from Streptomyces avermitilis: The Basis for Ordered Substrate Addition" Biochemistry 2003 42, 2072-2080.

Member: American Chemical Society Awards: 2007 National Institutes of Health(NIH) Ruth L. Kirschstein National Research Service Award