Steven M. Theg

Steven Theg

Position Title
Professor

Unit
Department of Plant Biology, College of Biological Sciences

2225 Life Sciences Addition
Bio

Research Interests

Protein transport

Protein translocation across biological membranes, with a focus on chloroplast membranes. Mechanism of multimeric protein complex assembly. Chloroplast bioenergetics.

The current objectives of the research in the Theg lab are to understand the events surrounding the transport of proteins across biological membranes and their assembly into larger multimeric complexes. Most of the laboratory's efforts focus on protein trafficking and assembly in chloroplasts isolated from higher plants (often peas, but also Arabidopsis and N. benthamiana). 

These organelles represent an excellent model system in which to study cellular protein targeting as they are easily separated from other organelles, and retain a high level of metabolic activity after isolation. In addition, they contain a level of structural complexity that requires additional sorting of proteins within the organelle. In these sorting reactions, chloroplasts utilize different protein targeting paradigms which are individually used by other organelles. Consequently, lessons learned from the study of protein targeting to and within chloroplasts can be applied to a number of other polypeptide translocating systems.

We have also made recent forrays into the mechanism of thylakoid division and the biochemistry of stromule formation.

Grad Group Affiliations

  • Biochemistry, Molecular, Cellular and Developmental Biology
  • Biophysics
  • Plant Biology

Specialties / Focus

  • Biochemistry
  • Biochemistry and Molecular Recognition
  • Cell and Developmental Biology
  • Cell Biology
  • Molecular Biology, Biochemistry and Genomics
  • Molecular Genetics
  • Organelle and Membrane Biology
  • Plant Molecular Biology
  • Structural Biology, Membranes and Macromolecular Assembly

Courses

  • Bis 102 Structure and Function of Biomolecules, Fall
  • Bis 105 Biomolecules and Metabolism, Fall, Spring
  • MCB 120L Biochemistry Laboratory, Fall
  • PLB 105 Plant Physiology, Fall

Professional Societies

  • American Association for the Advancement of Science
  • American Society of Plant Physiologists

Degrees and Awards

  • 1977 BS Biology Boston College
  • 1981 PhD Molecular Biophysics Florida State University
  • 2019 Fellow of the American Association for the Advancement of Science

Publications

Ganesan I, and Theg S.M. (2019) Structural considerations of folded protein import through the chloroplast TOC/TIC translocons.  FEBS Lett. 2019 Mar;593(6):565-572. doi: 10.1002/1873-3468.13342. Epub 2019 Mar 5.

Theg, S.M. (2018) Chloroplast transport and import.  Photosynth. Res. 138:261-262.  PMID: 30397741.

Asher A, Ganesan I, Klasek L, Theg SM. (2018) Isolation of physiologically active thylakoids and their use in energy-dependent protein transport assays. J. Vis. Exp. Sep 28; (139).  doi: 10.3791/58393.

Day, P.M. and Theg, S.M. (2108) Evolution of protein transport to the chloroplast envelope membranes.  Photosynth. Res. 138:315-326.  doi:10.1007/s11120-018-0540-x

Ganesan, I., Shi, L.-X., Labs, M., and Theg, S.M. (2018) Evaluating the functional pore size of chloroplast TOC and TIC protein translocons: Import of folded proteins.  Plant Cell 30:2161-2173.  Also bioRxiv 188052; doi: https://doi.org/10.1101/188052.

Ganesan, I., Shi, L.-X., Labs, M., and Theg, S.M. (2018) Evaluating the functional pore size of chloroplast TOC and TIC protein translocons: Import of folded proteins.  Plant Cell 30:2161-2173.  Also bioRxiv 188052; doi: https://doi.org/10.1101/188052.

Ganesan, I., Shi, L.-X., Labs, M., and Theg, S.M. (2018) Evaluating the functional pore size of chloroplast TOC and TIC protein translocons: Import of folded proteins.  Plant Cell 30:2161-2173.  Also bioRxiv 188052; doi: https://doi.org/10.1101/188052.

Yang, H., Pu, X., Wang, L,. Liu, L. and Theg, S.M. (2017) A new fluorescence-based method to monitor the pH in the thylakoid lumen using GFP variants. Biochem Biophys Res Commun. 486: 1-5. doi: 10.1016/j.bbrc.2016.12.032.

Ho, J., Kwan, W., Li, V. and Theg, S.M. (2017) Characterization of Thylakoid Division Using Chloroplast Dividing Mutants in Arabidopsis.  bioRxiv 200667; doi: https://doi.org/10.1101/200667

Ho, J. and Theg, S.M. (2015) The Formation of Stromules In Vitro from Chloroplasts Isolated from Nicotiana Benthamiana. PLOS ONE doi:10.1371/journal.pone.0146489 

Wang, X, Wei, Y., Shi, L-X., Ma, X and Theg, S.M. (2015) New Isoforms and Assembly of Glutamine Synthetase in the Leaf of Wheat (Triticum aestivum L.).  J. Exp. Bot. 66:6827-6834.  doi: 10.1093/jxb/erv388

Liu, L., McNielage, R.T., Shi, L.-X. and Theg, S.M. (2014) ATP requirement for chloroplast protein import is set by the Km for ATP hydrolysis of the stromal Hsp70 in Physcomitrella patens.  Plant Cell 26: 1246-1255.  doi: 10.1105/tpc.113.121822

Bricker, T.M., Bell, A.J., Tran, L. Frankel, L.K. and Theg, S.M. (2013) Photoheterotrophic growth of Physcomitrella patens.  Planta 293: 605-613.  doi:  10.1007/s00425-013-2000-3

Shi, L-X. and Theg, S.M. (2013) The energetic cost of protein import across the envelope membranes of chloroplasts.  Proc. Natl. Acad. Sci. USA, 110:930-935.

Shi, L-X. and Theg, S.M. (2013) The chloroplast protein import system: From algae to trees.  Biochim. Biophys. Acta  1833:314–331.

Lo, S.M. and Theg, S.M. (2012) Role of Vesicle-Inducing Protein in Plastids 1 in cpTat Transport at the Thylakoid. The Plant J. 71:656-668.

Shi, L-X. and Theg, S.M. (2011) The motors of protein import into chloroplasts. Plant Signaling & Behavior 6:1397-1401.

Theg, S.M. and Tom, C. (2011) Measurement of the ΔpH and electric field developed across Arabidopsis thylakoids in the light. Methods Mol. Biol. 775:327-357.

Shi, L-X. and Theg, S.M. (2010) A Stromal Hsp70 System Functions in Protein Import into Chloroplasts in the Moss Physcomitrella patens. The Plant Cell 22:1-16.

Lo, S.M. and Theg, S.M.(2010) Protein Targeting Across and Into Chloroplast Membranes. Methods Mol. Biol. 684:139-157.

Theg, S.M. (2010) Measurement of the Energetics of Protein Transport across the Chloroplast Thylakoid Membrane. Methods Mol. Biol. 619:323-337.

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