Prof. Dr. Susana Andrade

The transport of ammonium across biological membranes is carried out by a highly specialized family of integral membrane proteins, called Ammonium Transport (Amt) proteins. In prokaryotes and plants, import is used for biosynthetic purposes. In animals, both export and import functions are described for the Rhesus proteins - the Amt homologs in higher vertebrates - fulfilling nitrogen detoxification and pH homeostasis functions.

We are interested in understanding the mechanistic details that regulate the function of membrane proteins in general and of Amt proteins in particular.  For this we use X-ray crystallography to determine protein structures at high-resolution in combination with functional studies where purified protein is reconstituted into artificial membrane systems – proteoliposomes – for fast kinetic measurements and voltage clamp experiments by electrophysiology in planar lipid bilayers.

A further interesting aspect of ammonium transport in nitrogen metabolism is the close association of most prokaryotic Amt proteins with small, regulatory proteins of the P_II family. These proteins play a central role in signal transduction and integration events that balance the action of nitrogen uptake and utilization. As such they are able to block Amt transport by complex formation.  Once more we combine high-resolution structural analysis with isothermal calorimetric titrations to investigate the details of this signaling process and the factors that modulate Amt-GlnK complex formation.

10 selected publications

• Signaling ammonium across membranes through an ammonium sensor histidine kinase.
  Pflüger T, Hernández CF, Lewe P, Frank F, Mertens H, Svergun D, Baumstark MW, Lunin VY, Jetten MSM and Andrade SLA (2018).
  Nature Commun., 9, 164.
• A bound intermediate sheds light on the mechanism of nitrogenase.
  Sippel D, Rhode M, Netzer J, Trncik C, Gies J, Grunau K, Djurdjevic I, Decamps L, Andrade SLA and Einsle O (2018).
  Science, 359, 1484-1489.
• Global analysis of complex PELDOR time traces.
  Rein S, Lewe P, Andrade SLA, Kacprzak S, Weber S (2018).
  J. Magn. Reson., 295, 17-26.
• Nitrogenase FeMoco onvestigated by spatially-resolved anomalous dispersion refinement.
  Spatal T, Schleisier J, Burger E-M, Sippel D, Zhang L, Andrade SLA, Rees DC, Einsle O (2016).
  Nature Commun., 7, 10902.
• Direct Observation of Electrogenic NH₄⁺ Transport in Ammonium Transport (Amt) Proteins.
  Wacker T, Garcia-Celma J., Lewe P. and Andrade SLA (2014).
  Proc Natl Acad Sci U S A. 111(27):9995-10000.
• Analysis of the Magnetic Properties of Nitrogenase FeMo cofactor by Single-Crystal EPR Spectroscopy.
  Spatzal T, Einsle O and Andrade SLA (2013).
  Angew. Chem. Intl. Ed., 52(38), 10116-10119
• Fluorescent Sensors Reporting the Activity of Ammonium Transceptors in Live Cells.
  DeMichele R, Ast C, Loqué D, Ho CH, Andrade SLA, Lanquar V, Grossmann G, Gehne S, Kumke MU and Frommer WB (2013).
  eLife, 2, e00800.
• Structure and Mechanism of the Nitrite Channel NirC.
  Lü W, Schwarzer N, Du J, Gerbig-Smentek E, Andrade SLA, Einsle O (2012).
  Proc. Natl. Acad. Sci. USA, 109(45), 18395-18400.
• The Formate Channel FocA Exports the Products of Mixed-Acid Fermentation.
  Lü W, Du J, Schwarzer N, Gerbig-Smentek E, Einsle O, Andrade SLA (2012).
  Proc. Natl. Acad. Sci. USA, 109, 13254-13259.
• pH-dependent Gating in a FocA Formate Channel.
  Lü W, Du J, Wacker T, Gerbig-Smentek E, Andrade SLA, Einsle O (2011).
  Science 332, 352-354.