Janice L. Robertson, PhD

Associate Professor
Biochemistry and Molecular Biophysics

Biochemistry, Biophysics, and Structural Biology Program
Computational and Systems Biology Program
Neurosciences Program

  • 314-273-7758

  • 314-273-1682

  • MCD 223

  • janice.robertson@wustl.edu

  • https://www.robertsonlaboratory.com

  • membrane protein; single-molecule; TIRF microscopy; protein folding; thermodynamics; lipids; oligomerization

  • To understand how and why membrane proteins fold, form stable complexes, and achieve conformational stability inside of the oil-filled cell membrane.

Research Abstract:

The goal of my laboratory’s research is to provide a quantitative understanding of the reactions of membrane proteins in lipid bilayers through an integration of membrane protein biochemistry, single-molecule fluorescence microscopy and computational modeling. By combining these disciplines, we are developing new approaches to investigate several long-standing questions in this field.

First, we are studying the thermodynamic basis of membrane protein association in lipid membranes. In many cases of soluble protein association, binding is driven by the hydrophobic effect, an entropic drive that arises from burying greasy residues away from water. However, this cannot apply to the association of membrane proteins as membranes are comprised of oil. Why then do greasy membrane proteins choose to interact with other greasy protein surfaces over the similarly greasy lipid solvent? Recently, we developed a method to measure the free energy of association of high-affinity membrane protein complexes by passive dilution using single-molecule microscopy approaches (Chadda & Robertson, MIE 2016). We have applied this to study the dimerization of the large CLC-ec1 antiporter, showing that it is one of the most stable membrane protein complexes studied so far (Chadda et al., eLife 2016; Chadda et al., JGP 2018; Cliff et al., BBA-Biomembranes 2020). We are now using this as a model system for dissecting the thermodynamic driving forces underlying this strong affinity, and identifying how changes in protein (Mersch et al., J. Mol. Biol. 2021) or lipids (Chadda, Bernhardt et al. eLife 2021) affect the reaction. In the past, this research has been supported by NIH K99/R00 GM101016 and a Carver Trust Young Investigator Award, and it is currently supported by NIH R01 GM120260 renewed in 2021.

Second, we are extending our methods to study membrane protein regulation. In the context of the native cell membrane, ion channels and transporters do not exist as isolated units, but are instead in complex with small, membrane-embedded regulatory subunits that are critical for proper physiological function. For example, Na+, K+ and Cl- channels all associate with small single- or double-pass transmembrane helix regulatory proteins that have significant functional implications. However, in all of these cases, we lack an understanding of the equilibrium association reaction, which must be known if we wish to understand the regulatory nature of these assemblies. In this project, we will measure the equilibrium reactions of these regulatory complexes in a reconstituted system using single-molecule fluorescence imaging. From this, we will obtain the key binding information such as the equilibrium constant, stoichiometry and specificity of binding. In addition, we will learn how pharmacological modulators and disease-causing mutations alter these reactions. This research was previously supported by a Research Program of Excellence grant from the Iowa Neuroscience Institute, University of Iowa.

Finally, we are studying the synthesis and initial folding of membrane proteins in the cell. Using the sensitivity of single- molecule fluorescence microscopy directly in E. coli, we are identifying the genetic vs. protein discriminators against eukaryotic membrane protein expression in prokaryotic systems. The end goal of this project is to develop an optimization algorithm that will allow any scientist to take a poorly expressing mammalian membrane protein in E. coli, and increase expression to yields that will allow for structure determination by cryo-EM. This research was supported by NIH R21 GM126476.

Mentorship and Commitment to Diversity Statement:
Throughout my training, I have become aware of the significant inequities that lead to under-representation of people in science. Not only is this inherently wrong, but it is fundamentally in conflict with the mission of scientific discovery. The purpose of scientific research is to have the brightest minds study and solve challenging global problems, and this involves people from all backgrounds, not just those with the fewest barriers. Thus, one of my career goals is to correct inequities and foster an environment in which scientists from all backgrounds can excel. In my own lab, this means providing a safe and enriching environment where all people feel accepted. Beyond my lab, I make every effort to promote inclusion and representation of all scientists, pledging gender equity in speaker lists at the conferences that I have been nominated to organize (SGP, GRC, BPS) and providing opportunities for early-career under-represented scientists to attend through invited talks and travel awards. In addition, I was fortunate to be elected as a councilor of the SGP and have been working on the DEI committee to build initiatives such as the Excelsior award for early-career scientists and the Sharona Gordon award for transformational leadership. Finally, I recognize that success in this area requires educating myself and learning from others who have experienced inequity first hand. I am committed to learning from my colleagues and experts in the field to improve the climate.

Selected Publications:

Ernst M & Robertson JL (2021). The role of the membrane in transporter assembly and function. Journal of Molecular Biology, Jun 14:167103. doi: 10.1016/j.jmb.2021.167103.

Heath GR, Kots E, Robertson JL, Miyagi A, Lansky S, Lin YC, Khelashvili G, Weinstein H, Scheuring S (2021). Localization Atomic Force Microscopy. Nature, Jun;594(7863):385-390. doi: 10.1038/s41586- 021-03551-x.

Mersch K, Ozturk TN, Park K, Lim HH, Robertson JL (2021). Altering CLC stoichiometry by reducing non-polar side-chains at the dimerization interface. J Mol Biol. 2021 Apr 16:433(8):166886. doi: 10.1016/j.jmb.2021.166886.

Chadda R, Bernhardt N, Kelley EG, Teixeira SCM, Griffith K, Gil-Ley A, Ozturk TN, Hughes LE, Forsythe A, Krishnamani V, Faraldo-Gómez J & Robertson JL (2021). Dimerization of a membrane transporter is driven by differential energetics of lipid solvation of dissociated and associated states. eLife 10, e63288. PMID: 33825681.

Cliff L, Chadda R & Robertson JL (2020). Occupancy distributions of membrane proteins in heterogeneous liposome populations. Biochim Biophys Acta Biomembr. 2020 Jan 1;1862(1):183033. doi:10.1016/j.bbamem.2019.183033, PMID: 31394099, PMCID: PMC6899186.

Robertson JL (2019). Interrogating the conformational dynamics of BetP transport. Journal of General Physiology, 151(3): 279-281. doi:10.1085/jgp.201812315.

Robertson JL (2019). Membrane physiologists of all kinds meet at Woods Hole. Journal of General Physiology, 151(3):273. doi:10.1085/jgp.201912340

Chadda R, Cliff L, Brimberry M & Robertson JL (2018). A model-free method for measuring dimerization free energies of CLC-ecl in lipid bilayers. Journal of General Physiology. 2018 Jan 10, doi: 10.1085/jgp.201711893, PMID: 29321261. Commentary by KF Fleming, "Taking deterministic control of membrane protein monomer-dimer measurements" J. Gen Physiol. 2018 Jan 17, pii: jgp.201711913. doi: 10.1085/jgp201711913.

Robertson JL (2018). The lipid bilayer membrane and its protein constituents. Journal of General Physiology 150 ( 11). doi: 10.0185/jgp.201812153

Condon SGF✢, Mahbuba DA✢, Armstrong CR, Dias-Vazquez G, Craven SJ, LaPointe LM, Khadria AS, Chadda R, Crooks JA, Rangarajan N, Weibel DB, Hoskins AA, Robertson JL, Cui Q & Senes A (2017). The FtsLB sub-complex of the bacterial divisome is a tetramer with an uninterrupted FtsL helix linking the transmembrane and periplasmic regions. J Biol Chem. 2017 Dec 12, doi: 10.1074/jbc.RA117.000426

Chadda R & Robertson JL. (2016). Measuring Membrane Protein Dimerization Equilibrium in Lipid Bilayers by Single-Molecule Fluorescence Microscopy. Methods Enzymol. 581:53-82.

Chadda R & Robertson JL. (2016). Measuring Membrane Protein Dimerization Equilibrium in Lipid Bilayers by Single-Molecule Fluorescence Microscopy. Methods Enzymol. 581:53-82.

Chadda R, Krishnamani V, Mersch K, Wong J, Brimberry M, Chadda A, Kolmakova-Partensky L, Friedman LJ, Gelles J & Robertson JL (2016). The dimerization equilibrium of a ClC Cl-/H+ antiporter in lipid bilayers. eLife 2016; 10.7554/eLife.174382016. PMID: 27484630.

Stockbridge R, Robertson JL, Kolmakova-Partensky L, Miller C. (2013). A family of fluoride-specific ion channels with dual-topology architecture. eLife, 2013;2:e01084. DOI: 10.7554/eLife.01084.

Hyde HC, Sandtner W, Vargas E, Dagcan A, Robertson JL, Roux B, Correa A M & Bezanilla F. (2012) Nano-Positioning System for Structural Analysis of Functional Homomeric Proteins in Multiple Conformations. Structure, 20(10):1629-40.

Robertson JL, Palmer LG & Roux B. (2012). Multi-ion distributions in the cytoplasmic domain of inward-rectifier potassium channels. Biophysical Journal, 103(3), 434–443.

Kawate T, Robertson JL, Li M, Silberberg SD, and Swartz KJ. (2011). Ion access pathway to the transmembrane pore in P2X receptor channels. Journal of General Physiology, 137(6):579-90.

Jayaram H, Robertson JL, Wu F, Williams C & Miller C. (2011). Structure of a slow ClC transporter from cyanobacteria. Biochemistry 50(5):788-94. (24 citations to date). Corrigendum in Biochemistry 50(19), 4228.

Robertson JL (2011). We choose to go to the membrane. Proceedings of the National Academy of Sciences of the United States of America, 108(25), 10027-10028.

Robertson JL, Kolmakova-Partensky L & Miller C. (2010). Design, function and structure of a monomeric ClC transporter. Nature 468(7325):844-7.

Jogini V, Robertson JL & Roux B. (2010). Continuum electrostatics calculations of K+ Channels. Chapter 7, pp 177-202. Molecular Simulations and Biomembranes: From Biophysics to Function. The Royal Society of Chemistry.

Tan K, Sather A, Robertson JL, Moy S, Roux B & Joachimiak A. (2009). Structure of cytoplasmic pentameric pore of ZntB transporter from V. parahaemolyticus. Protein Science 18(10): 2043-52.

Robertson JL, Palmer LG & Roux B. (2008). Long-pore electrostatics in inward-rectifier potassium channels. Journal of General Physiology 132(6):613-32.

Robertson JL & Roux B. (2005) One channel: open and closed. Structure 12(10):1398-400.

Zhang YY, Robertson JL, Gray DA & Palmer LG. (2004). Carboxy-terminal determinants of conductance in inward-rectifier K+ channels. Journal of General Physiology 124(6):729-39.

Last Updated: 11/15/2021 2:31:05 PM

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