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Löw Group

Membrane Protein Structural Biology

Dr. Christian Löw

Group Leader

+49 40 8998 87570
christian.loew@cssb-hamburg.de

Home Institute

European Molecular Biology Laboratory
www.embl.de

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

PREVIOUS AND CURRENT RESEARCH

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.

Crystal structure of the oligopeptide transporter PepTSt in the inward open conformation at 2.0 Å resolution. Bound lipids and water molecules are illustrated.

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).

Binding and coordination of the tripeptide Phe-Ala-Gln in the inward open conformation of PepTSt.

FUTURE PROJECTS AND GOALS

  • 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.

Transporting a sugar molecule across the membrane. Conformational transitions of a sugar transporter from the outward open to the inward open state. The molecular movie is a morph of homologous sugar transporter X-ray structures captured in different states of the transport cycle.

Publications

2014

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

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

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,

2013

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.

Guettou F, Löw C, Quistgaard EM, Hedrén M, Frauenfeld J, Nordlund P, Haneskog L, Moberg P. (2013) Rapid screening of integral membrane proteins suitable for structure determination. Discovery Matters 16

2012

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.

Löw C, Stubbs MT, Haupt C, Balbach J (2012) Metallochaperone SlyD. Encyclopedia of Inorganic and Bioinorganic Chemistry. https://doi.org/10.1002/9781119951438.eibc2061

2011

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

Moberg P, Burstedt M, Nordlund P, Haneskog L, Löw C (2011) Stability of membrane proteins analyzed by gel filtration. Discovery Matters (13)

Löw C, Hedrén M, Nordlund P, Haneskog L, Moberg P (2011) Rapid buffer scouting and quality control of integral membrane proteins. Discovery Matters (12):10-11.

2010

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

2009

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 (2009) Energy Landscapes of Protein Folding: From Structure to Function. SVH Verlag, Saarbrücken.

2008

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

2007

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)

2006

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