Steven Vik

Stephen Vik portrait

Professor Emeritus

Biological Sciences


Office: DLSB 236
Phone: 214-768-4228

Educational Background

Ph.D. University of Oregon


Lab: DLSB 218
Tel: 214-768-2729 or 214-768-3896


Research Interests

Protein Structure and Function/ Biochemistry of Membrane-Bound Enzymes

Dr. Vik is interested in the structure, function, and assembly of the membrane-bound enzymes that are involved in oxidative phosphorylation. His research group is currently investigating Complex I from E. coli.

Complex I, the NADH-ubiquinone oxidoreductase in Escherichia coli is encoded by the thirteen genes of the nuo operon. It is homologous to the larger enzyme found in mammalian mitochondrial membranes. This enzyme oxidizes NADH, reduces ubiquinone, and translocates protons across the inner membrane. Six of the thirteen subunits (B, CD, E, F, G and I) constitute a membrane peripheral domain that includes the NADH binding site, one noncovalently bound flavin mononucleotide, and nine Fe-S centers. Subunits E, F, and G form the N module, which binds NADH. B, CD, and I make up the Q module, which helps to bind the quinone near the membrane, where it is reduced. The other seven subunits (A, H, J, K, L, M, and N) are hydrophobic membrane proteins that are homologous to the seven proteins typically encoded by mammalian mitochondrial DNA. These proteins form the P module, and contain 4 sites for proton translocation. The three largest of the mitochondrial homologues, called L, M and N in E. coli, are related to one another, and to proteins in a bacterial cation/proton antiporter system. Current work in the lab concerns the assembly pathway of these subunits, and consequences of clinically identified mutations on the assembly and function of Complex I.

Selected Publications

(at PubMed)

Amarneh, B. and Vik, S.B. (2003) Mutagenesis of Subunit N of the Escherichia coli Complex I. Identification of the Initiation Codon and the Sensitivity of Mutants to Decylubiquinone. Biochemistry 42, 4800-4808

Ishmukhametov, R.R., Galkin, M.A., and Vik, S.B.. (2005) Ultrafast purification and reconstitution of His-tagged cysteine-less Escherichia coli F1Fo ATP synthase. Biochim. Biophys. Acta 1706, 110-116.

Amarneh, B. and Vik, S.B. (2005) Direct Transfer of NADH From Malate Dehydrogenase to Complex I in Escherichia coli. Cell Biochem. Biophys. 42, 251-262

Amarneh B., De Leon-Rangel J., and Vik S. B. (2006) Construction of a deletion strain and expression vector for the Escherichia coli NADH:ubiquinone oxidoreductase (Complex I). Biochim. Biophys. Acta. 1757: 1557-1560

Vik, S.B. (19 October 2007). Chapter 3.2.3, ATP Synthesis by Oxidative Phosphorylation. In A. Böck, R. Curtiss III, J. B. Kaper, F. C. Neidhardt, T. Nyström, K. E. Rudd, and C. L. Squires (ed.), EcoSal-Escherichia coli and Salmonella: cellular and molecular biology. [Online.] ASM Press, Washington, D.C.(doi: 10.1128/ecosal.3.2.3)

Vik, S.B. (February 2008). Chapter 2, An analysis of the structure and function of Complex I from Escherichia coli. In M. I. Gonzalelz Siso (ed.), Complex I and Alternative Dehydrogenases. Transworld Research Network, Kerala, India.

Amarneh, B., and Vik, S.B. (2010) Transmembrane topology of subunit N of Complex I (NADH:Ubiquinone Oxidoreductase) from Escherichia coli. J. Bioenerg. Biomembr. 42: 511-516.

Michel, J., DeLeon-Rangel, J., Zhu, S., Van Ree, K., and Vik, S.B. (2011) Mutagenesis of the L, M, and N subunits of Complex I from Escherichia coli indicates a common role in function. PLoS One 6: e17420.

Vik, S.B. (2011) The transmembrane helices of the L, M, and N subunits of Complex I from E. coli can be assigned on the basis of conservation and hydrophobic moment analysis. FEBS Lett. 585: 1180-1184.

Li, Bo,. Vik, S. B., Tu, Y. (2012) Theaflavins inhibit the ATP synthase and the respiratory chain without increasing superoxide production. J. Nutr. Biochem. 23: 953-960.

 Zhu, S., and Vik, S.B. (2015) Constraining the Lateral Helix of Respiratory Complex I by Cross-linking Does Not Impair Enzyme Activity or Proton Translocation. J. Biol. Chem. 290, 20761-20773.

Zhu, S., Canales, A., Bedair, M., and Vik, S.B. (2016) Loss of Complex I activity in the Escherichia coli enzyme results from truncating the C-terminus of subunit K, but not from cross-linking it to subunits N or L. J. Bioenerget. Biomembr. 48, 325-333.

Tursun, A., Zhu, S., and Vik, S.B. (2016) Probing the proton channels in subunit N of Complex I from Escherichia coli through intra-subunit cross-linking. Biochim Biophys Acta. 1857, 1840-1848.

Galkin, M.A., Russell, A.N., Vik, S.B., Berry, R.M., Ishmukhametov, R.R. Detergent-free Ultrafast Reconstitution of Membrane Proteins into Lipid Bilayers Using Fusogenic Complementary-charged Proteoliposomes.. J. Vis. Exp. (134), e56909, (2018). doi:10.3791/56909


National Institutes of Health, American Heart Association


  • 1975 B.S. Chemistry, California Institute of Technology
  • 1980 Ph.D. Chemistry, University of Oregon

Professional Experience


Postdoctoral Fellow, Department of Biochemistry, Scripps Clinic and Research Foundation, La Jolla, CA


Visiting Research Scholar, Chinese Academy of Sciences, Institute of Zoology, Beijing, China


Postdoctoral Research Fellow, Department of Biological Sciences, Stanford University, Stanford, CA


Assistant Professor, Department of Biological Sciences, Southern Methodist University, Dallas, TX


Associate Professor, Department of Biological Sciences, Southern Methodist University, Dallas, TX


Professor, Department of Biological Sciences, Southern Methodist University, Dallas, TX


Visiting Scientist, Universität Osnabrück, Osnabrück, Germany


Visiting Professor, Department of Tea Science, Zhejiang University, Hangzhou, China


Chair, Department of Biological Sciences, Southern Methodist University, Dallas, TX


Visiting Scientist, Universität Osnabrück, Osnabrück, Germany

Editorial Board

Journal of Biological Chemistry 2005-2010, 2012-2017