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Löw Group

Membrane Protein Structural Biology

Dr. Christian Löw

Group Leader

+49 40 8998 87570

Home Institute

European Molecular Biology Laboratory

Using innovative biophysical and biochemical methods, the Löw group aims to enhance the understanding of nutrient uptake. Combining high throughput technologies with classical biochemical approaches we seek to develop a better understanding and visualization of the molecular processes of how nutrients and drugs are transported across a lipid bilayer.

Research Projects


Cell membranes compartmentalise metabolic processes and serve as selective barriers for permeation. Therefore, nutrient transport through the plasma membrane is essential to maintain homeostasis within the cell. Many proton-coupled secondary active transporters of the major facilitator superfamily (MFS) are involved in the accumulation of nutrients above extracellular levels. Structural and functional analyses of MFS transporters suggest an alternating-access mechanism for the transport of substrates across the membrane. Here the transporter adopts different conformational states, allowing the substrate binding site to face either side of the membrane. Since MFS transporters are found in all branches of life and often with numerous gene copies, we believe that many if not all of these transporters follow a common transport mechanism.

Proton coupled oligopeptide transporters of the PepT family (also known as the POT or SLC15 family) are responsible for the uptake of a range of different di- and tripeptides, derived from the digestion of dietary proteins, and are highly conserved in all kingdoms of life. The best studied members of this family include the two human peptide transporters, PepT1 and PepT2. Both are also of great pharmacological and pharmaceutical interest as they accept a number of drugs and amino acid-conjugated pro-drugs as substrates. A detailed understanding of the structural basis for substrate recognition can therefore help to convert pharmacologically active compounds into substrates for PepT1 and PepT2 and improve their absorption in the small intestine and subsequent distribution in the body. We therefore study members of the proton-dependent oligopeptide transporter (POT) family in vitro and in vivo using a combination of structural biology methods (X-ray, cryo EM, crystallization chaperones) with biochemical approaches (transport assays, fluorescence spectroscopy, crosslinking, transcriptomics).


  • Characterisation of pro- and eukaryotic nutrient transporters in various states of the transport cycle using X-ray crystallography and/or Cryo-EM to decipher a common transport mechanism of MFS transporters.
  • Structural and dynamic insights into the binding mode of POTs to peptides, drugs, and inhibitors.
  • Insights into structure and function of transport regulators of nutrient transporters by structural systems biology approaches


Integral membrane proteins are a challenging class of proteins in terms of their structural and functional characterisation. Over the years we have developed and established new tools and a workflow for protein production and quality control of membrane proteins including functional assays. Furthermore, we are developing new ways to stabilize integral membrane proteins in vitro upon extraction from their natural environment.

Research Team


Group Leader

Dr. Christian Löw
Phone:+49 40 8998 87570


Kim Bartels
Phone:+49 40 8998 87580


Dr. Katharina Jungnickel
Phone:+49 40 8998 87571


Maxime Killer
Phone:+49 40 8998 87580


Samuel Pazicky
Phone:+49 40 8998 87571


Joanna Pieprzyk
Phone:+49 40 8998 87579


Dr. Juliane Wunderlich
Phone:+49 40 8998 87580




Wichers JS, Scholz JAM, Strauss J, Witt S, Lil lA, Ehnold LI, Neupert N, Liffner B, Lühken  R, Petter M, Lorenzen S, Wilson DW, Löw C, Lavazec C, Bruchhaus I, Tannich E, Gilberger  TW, Bachmann A (2019) Dissecting the Gene Expression, Localization, Membrane Topology, and Function of the Plasmodium falciparum STEVOR Protein Family. MBio.; pii: e01500-19. doi:  https://doi.org/10.1128/mBio.01500-19, PMID: 31363031

Kotov, V, Bartels, K, Veith, K, Josts, I, Subhramanyam, UKT, Günther, C, Labahn, J, Marlovits, TC, Moraes, I, Tidow, H, Löw, C and Garcia-Alai, MM (2019) High-throughput stability screening  for detergent-solubilized membrane proteins. Sci Rep. 17;10379. doi: https://doi.org/10.1038/s41598-019-46686-8, PMID: 31316088

Ural-Blimke Y, Flayhan A, Strauss J, Rantos V, Bartels K, Nielsen R, Pardon E, Steyaert J, Kosinski J, Quistgaard EM, Löw C# (2019) Structural basis of (pro)drug transport in the SLC15 family of peptide transporters. J Am Chem Soc.141; 2404-2412. doi: https://doi.org/10.1021/jacs.8b11343, PMID: 30644743


Pieprzyk J, Pazicky S, Löw C# (2018) Transient Expression of Recombinant Membrane-eGFP Fusion Proteins in HEK293 Cells. Methods Mol Biol. 1850:17-31. doi: https://doi.org/10.1007/978-1-4939-8730-6 2, PMID: 30242677

Molledo MM*, Quistgaard EM*, Löw C# (2018) Tripeptide binding in a proton-dependent oligopeptide transporter. FEBS Letters 592: 3239-3247. doi: https://doi.org/10.1002/1873-3468.13246 PMID: 30194725

Hajizadeh NR*, Pieprzyk J*, Skopintsev P, Flayhan A, Svergun DI #, Löw C# (2018) Probing the architecture of a multi-PDZ domain protein: structure of PDZK1 in solution. Structure 26: 1522-1533.e5. doi: https://doi.org/10.1016/j.str.2018.07.016, PMID: 30220543

Molledo MM *, Quistgaard EM *, Flayhan A, Pieprzyk J, Löw C# (2018) Multispecific substrate recognition in a proton-dependent oligopeptide transporter. Structure 26:467-476.e464. doi: https://doi.org/10.1016/j.str.2018.01.005, PMID: 29429879

Flayhan A, Mertens H, Ural-Blimke H, Molledo MM, Svergun DI, Löw C# (2018) Saposin lipid nanoparticles: a highly versatile and modular tool to reconstitute membrane proteins. Structure 26:345-355.e345. doi: https://doi.org/10.1016/j.str.2018.01.007, PMID: 29413323


Veith K, Molledo MM, Hernandez YA, Josts I, Nitsche J, Löw C#, Tidow H # (2017) Lipid-like peptides can stabilize integral membrane proteins for biophysical and structural studies. ChemBioChem 18:1735-1742. doi: https://doi.org/10.1002/cbic.201700235, PMID: 28603929

Quistgaard EM, Molledo MM, Löw C# (2017) Structure determination of a major facilitator peptide transporter: Inward facing PepTSt from Streptococcus thermophilus crystallized in space group P3121. PLoS One, 12:e0173126. doi: https://doi.org/10.1371/journal.pone.0173126, PMID: 28264013


Quistgaard E M, Löw C, Guettou F, Nordlund P (2016) Understanding transport by the major facilitator superfamily (MFS): structures pave the way. Nature Reviews Molecular Cell Biology 17:123-132. doi: https://doi.org/10.1038/nrm.2015.25, PMID: 26758938

Quistgaard EM, Weininger U, Ural-Blimke Y, Modig K, Nordlund P, Akke M, Löw C# (2016) Molecular insights into substrate recognition and catalytic mechanism of the chaperone and FKBP peptidyl-prolyl isomerase SlyD. BMC Biology 14:82. doi: https://doi.org/10.1186/s12915-016-0300-3, PMID: 27664121

Frauenfeld J, Löving R, Armache JP, Sonnen A, Guettou F, Moberg P, Zhu L, Jegerschöld C, Flayhan A, Briggs JA, Garoff H, Löw C, Cheng Y,Nordlund P (2016) A saposin-lipoprotein nanoparticle system for reconstituting membrane proteins. Nature Methods 13:345-351. doi: https://doi.org/10.1038/nmeth.3801, PMID: 26950744


Guettou F, Quistgaard EM, Raba M, Moberg P, Löw C, Nordlund P (2014) Selectivity mechanism of a bacterial homolog of the human drug-peptide transporters PepT1 and PepT2. Nature Structural and Molecular Biology 21:728-731. doi: https://doi.org/10.1038/nsmb.2860, PMID: 25064511

Dovega R, Tsutakawa S, Quistgaard EM, Anandapadamanaban M, Löw C, Nordlund P (2014) Structural and biochemical characterization of human PR70 in isolation and in complex with the scaffolding subunit of protein phosphatase 2A. PLoS ONE 9:e101846. doi: https://doi.org/10.1371/journal.pone.0101846, PMID: 25007185

Löw C#, Quistgaard EM, Kovermann M, Anandapadamanaban M, Balbach J, Nordlund P #  (2014) Structural basis for PTPA interaction with the invariant C-terminal tail of PP2A. Biological Chemistry 395:881-889. doi: https://doi.org/10.1515/hsz-2014-0106, PMID: 25003389


Löw C #, Yau YH, Pardon E, Jegerschöld C, Wåhlin L, Quistgaard EM, Moberg P, Geifman-Shochat S, Steyaert J, Nordlund P # (2013) Nanobody mediated crystallization of an archeal mechanosensitive channel. PLoS One, e77984.

Quistgaard EM, Löw C, Moberg P, Nordlund P Metal-mediated crystallization of the xylose transporter XylE from Escherichia coli in three different crystal forms. J Struct Biol. 184; 375-8.

Quistgaard EM, Löw C, Moberg P, Guettou F, Maddi K, Nordlund P (2013) Structural and biophysical characterization of the cytoplasmic domains of human BAP29 and BAP31. (2013) PLoS One, e71111.

Guettou F, Quistgaard EM, Trésaugues L, Moberg P, Jegerschöld C, Zhu L, Jong AJ, Nordlund P #, Löw C # (2013) Structural insights into substrate recognition in proton-dependent oligopeptide transporters. EMBO Rep 14, 804-10.

Weininger U, Respondek M, Löw C, Akke M (2013) Slow aromatic ring flips detected despite near-degenerate NMR frequencies of the exchanging nuclei. J Phys Chem B 117, 9241-7.

Quistgaard EM *, Löw C *, Moberg P, Tresaugues L, Nordlund P (2013) Structural basis for substrate translocation in the GLUT homology family of monosaccharide transporters. Nature Structural and Molecular Biology 20, 766-8.

Löw C #*, Moberg P *, Quistgaard EM, Hedrén M, Guettou F, Frauenfeld Haneskog L, Nordlund P # (2013) High-throughput analytical gel filtration screening of integral membrane proteins for structural studies. Biochim Biophys Acta. 1830, 3497-508.


Quistgaard EM, Nordlund P #, Löw C # (2012) High-resolution insights into binding of unfolded polypeptides by the PPIase chaperone SlpA. FASEB Journal 26, 4003-4013.

Löw C #, Jegerschöld C, Kovermann M, Moberg P, Nordlund P # (2012) Optimisation of over-expression and biophysical characterisation of human membrane protein synaptogyrin 1. PLoS One, e38244.


Klepsch M, Kovermann M, Löw C, Balbach J, Permentier HP, Fusetti F, de Gier JW, Slotboom DJ, Berntsson RP (2011)Escherichia coli binding protein OppA has a preference for positively charged peptides. Journal of Molecular Biology 414, 75-85

Kahra D, Kovermann M, Löw C, Hirschfeld V, Haupt C, Balbach J, Hübner C (2011) Conformational plasticity and dynamics in a generic protein folding catalyst unraveled by single-molecule FRET. Journal of Molecular Biology 411, 781-90

Kovermann M, Zierold R, Haupt C, Löw C, Balbach J (2011) NMR relaxation unravels interdomain crosstalk of the two domain prolyl isomerase and chaperone SlyD. Biochim. Biophys. Acta.  1814, 873-81


Löw C, Neumann P, Tidow H, Weininger U, Haupt C, Friedrich-Epler B, Scholz C, Stubbs MT, Balbach J (2010) Crystal Structure Determination and Functional Characterization of the Metallochaperone SlyD from Thermus thermophilus. Journal of Molecular Biology 398, 375-390


Weininger U, Zeeb M, Neumann P, Löw C, Stubbs MT, Lipps G, Balbach J (2009) Structure based stability analysis of an extremely stable dimeric DNA binding protein from Sulfolobus islandicus. Biochemistry 48, 10030-7

Schulenburg C, Löw C, Weininger U, Mrestani-Klaus C, Hofmann H, Balbach J, Ulbrich-Hofmann R, Arnold U (2009) The folding pathway of Onconase is directed by a conserved intermediate. Biochemistry 48, 8449-57

Hofmann H, Weininger U, Löw C, Golbik RP, Balbach J, Ulbrich-Hofmann R (2009) Fast amide proton exchange reveals close relation between native-state dynamics and unfolding kinetics. J Am Chem Soc. 14, 140-146

Löw C, Homeyer N, Weininger U, Sticht H, Balbach J (2009) Conformational Switch upon Phosphorylation: Human CDK Inhibitor p19INK4d Between Native and Intermediate State. ACS Chem Biol. 16, 53-63 (2009); PMID: 19063602. – (“Pionts of view”- Doug Barrick. Biological Regulation via Ankyrin Repeat Folding. ACS Chem Biol. 16, 19-22


Löw C, Weininger U, Lee H, Schweimer K, Neundorf I, Beck-Sickinger AG, Pastor RW, Balbach J (2008) Structure and Dynamics of Helix-0 of the N-BAR Domain in Lipid Micelles and Bilayers. Biophys J. 95, 4315-23

Löw C, Weininger C, Neumann P, Klepsch M, Lilie H, Stubbs MT, Balbach J (2008) Structural Insights into an Equilibrium Folding Intermediate of an Archaeal Ankyrin Repeat Protein. Proc. Natl. Acad. Sci. 105, 3779-3784


Schulenburg C, Martinez-Senac MM, Löw C, Golbik RP, Ulbrich-Hofmann R, Arnold U (2007) Identification of three Phases in Onconase Refolding. FEBS Journal 274, 5826-5833

Löw C, Weininger U, Zeeb M, Zhang W, Laue ED, Schmid FX, Balbach J (2007) Folding Mechanism of an Ankyrin Repeat Protein: Scaffold and Active Site Formation of Human CDK Inhibitor p19INK4d. Journal of Molecular Biology 373, 219-231 (Faculty of 1000 - evaluation)


Zeeb M, Max KEA, Weininger U, Löw C, Sticht H, Balbach, J (2006)Recognition of T-rich single-stranded DNA by the Cold Shock Protein Bs-CspB in Solution. Nucl. Acids Res. 34, 4561-4571