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Johns Hopkins University logoProgram in Molecular Biophysics
Steven Rokita 

Dr. Steve Rokita

Department of Chemistry
Krieger School of Arts & Sciences

B.S. 1979, University of California, Berkeley
Ph.D. 1983, Massachusetts Institute of Technology

124 Remsen Hall
3400 N. Charles Street
Baltimore, MD 21218

Office: 410-516-5793
Lab: 410-516-8776


School of Arts & Sciences logo

Our research program is united by a common interest in describing the structure and activity of biological macromolecules through their essential chemical reactivity.  The methods of biophysics, biochemistry and organic chemistry are applied to questions on enzyme catalysis and nucleic acid modification. Current projects include enzymatic dehalogenation and reversible covalent chemistry expressed by quinone methide intermediates.

Organohalides are distributed widely in the environment and originate from both biological and industrial sources.  Under aerobic conditions, these compounds are typically consumed by oxidative and hydrolytic metabolism.  However, animals also express the unusual ability to promote reductive dehalogenation of natural iodotyrosine derivatives related to the thyroid hormone thyroxine.  Iodide recovery from these compounds is promoted by iodotyrosine deiodinase, an enzyme crucial for human health.  Investigations are currently designed to understand the mechanism of this enzyme and the role of its bound flavin in catalysis.  Flavin-dependent reactions are associated with a wide variety of metabolic transformations but its use in reductive dehalogenation is quite rare. Results of this research will help to expand the known repertoire of flavin chemistry and will guide its future use in bioremediation of organohalide pollutants.

Selected Publications 

Fakhari, F. and S. E. Rokita (2014) A Walk Along DNA Using Bipedal Migration of a Dynamic and Covalent Cross-linker. Nature Commun.5:5591

Hu, J., Chuenchor, W. and S. E. Rokita (2015) A Switch Between One- and Two-Electron Chemistry of the Human Flavoprotein Iodotyrosine Deiodinase is Controlled by Substrate. J. Biol. Chem. 290:590-600.

Bobyk, K.D., Ballou, D.P. and S.E. Rokita (2015) Pre-steady-state characterization of iodotyrosine deiodinase from human thyroid. Biochemistry 54:4487-4494.

Lonnberg, T., Hutchinson, M. and S.E. Rokita (2015) Selective alkylation of C-rich bulge motifs in nucleic acids by quinone methide derivatives.  Chem. Eur. J. 21:13127-13186.

Phatarphekar, A., Buss, J.M., and S.E. Rokita. (2014) Iodotyrosine Deiodinase:  A Unique Flavoprotein Present in Organisms of Diverse Phyla. Mol. BioSyst. 10:86-92.

Campbell, N.P. and S.E. Rokita. (2014) Electron Transport in DNA Initiated by Diaminonaphthalene Donors Alternatively Bound by Non-Covalent Association.  Org. Biomol.Chem.  12:1143-1148.

McCrane, M. P., Hutchinson, M. A., Ad, O. and S.E. Rokita. (2014) Oxidative Quenching of Quinone Methide Adducts Reveals Transient Products of Reversible Alkylation in Duplex DNA.  Chem. Res. Toxicol.  27:1282-1293.

Finch, A.S. Davis, W.B. and S.E. Rokita. (2013) Accumulation of the Cyclobutane Thymine Dimer in Defined Sequences of Free and Nucleosomal DNA.  Photochem. Photobiol. Sci 12:1474-1482.

Fakhari, F. Chen, Y-Y. K. and S.E. Rokita. (2013) Enhancing Excess Electron Transport in DNA. Chem. Commun. 49:7073-7075.

Buss, J.M., P.M. McTamney, and S.E. Rokita. (2012) Expression of a soluble form of iodotyrosine deiodinase for active site characterization by engineering the native membrane protein from Mus musculus. Protein Sci. 21:351-361.

Liu, Y., and S.E. Rokita (2012) Inducible alkylation of DNA by a quinone methide-peptide nucleic acid conjugate. Biochemistry 51:1020-1027.

McCrane, M.P., E.E. Weinert, Lin, Y., Mazzola, E.P., Lam, Y-F., Scholl, P.F., and S.E. Rokita. (2011) Trapping a labile adduct formed between an ortho-quinone methide and 2'-deoxycytidine. Org. Lett. 13:1186-1189.

Fakhari, M.A., and S.E. Rokita. (2011) A new solvatochromic fluorophore with high sensitivity for studying biopolymers. Chem. Commun. 47:4222-4224.

Rokita, S.E., J.M. Adler, P.M. McTamney, and J.A. Watson, Jr. (2010) Efficient use and recycling of the micronutrient iodide in mammals. Biochimie 92:1227-1235.

Rossiter, C.S., E. Modica, D. Kumar, and S.E. Rokita. (2011) Few constraints limit the design of quinone methide-oligonucleotide self-adducts for directing DNA alkylation. Chem. Commun. 47:1476-1478.

Wang, H., and S.E. Rokita. (2010) Dynamic cross-linking is retained in duplex DNA after multiple exchange of strands. Angew. Chem. Int. Ed. 49:5957-5960.

Thomas, S.R., P.M. McTamney, J.M. Adler, N. LaRonde-LeBlanc, and S.E. Rokita. (2009) Crystal structure of iodotyrosine deiodinase, a novel flavoprotein responsible for iodide salvage in thyroid glands. J. Biol. Chem. 284:19659-19667.

McTamney, P.M., and S.E. Rokita. (2008) A mammalian reductive deiodinase has broad power to dehalogenate chlorinated and brominated substrates. J. Am. Chem. Soc. 131:14212–14213.

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