ALBA II Colloquium - "Multilength scale imaging with cryo-EM"

by Hartmut Luecke (Center for Molecular Medicine Norway)

Monday 22 Feb 2021, 11:00 → 12:00 Europe/Madrid

ZOOM Videoconference (https://rediris.zoom.us/j/86417671246?pwd=NFJxNWh0MVhvWDM0cXRVSkZIODZvUT09)

Abstract

I will briefly discuss the various 3D structure determination techniques employed by structural biologists for structure-function studies of macromolecules. I will then highlight the special roadblocks one encounters when working with membrane proteins. Finally, I will present a specific project from my lab:

Helicobacter pylori chronic infection:

The evil duo of a pH-gated urea channel and a cytoplasmic Urease

Helicobacter pylori’s proton-gated plasma membrane urea channel and cytoplasmic urease are essential for the survival of this carcinogen the human stomach.  The channel is closed at neutral pH and opens at acidic pH to allow the rapid access of urea to cytoplasmic urease.  Urease hydrolyzes urea into 2 NH3 and CO2, neutralizing protons and thus buffering the cytoplasm even in gastric juice when the pH is below 2.0.  We determined the crystal structure of the channel, revealing six protomers assembled in a hexameric ring surrounding a central bilayer plug of ordered lipids.  Each protomer encloses a channel formed by a twisted bundle of six transmembrane helices.  The bundle defines a previously unobserved fold comprising a two-helix hairpin motif repeated three times around the central axis of the channel, without the inverted repeat of mammalian-type urea transporters.  Both the channel and the protomer interface contain residues conserved in the AmiS/UreI superfamily, suggesting the preservation of channel architecture and oligomeric state in this superfamily.  Predominantly aromatic or aliphatic side chains line the entire channel and define two consecutive constriction sites in the middle of the channel.  Mutation of Trp153 in the cytoplasmic constriction site to Ala or Phe decreases the selectivity for urea in comparison with thiourea, suggesting that solute interaction with Trp153 contributes specificity.  The structure suggests a new model for the permeation of urea and other small amide solutes in prokaryotes and archaea.  Follow-up microsecond-scale unrestrained molecular dynamics studies provide a detailed mechanism of urea and water transport by the channel.  More recently, we have determined the structure of the 1.1 MDa urease with various bound inhibitors to resolutions up to 1.68 Å using cryo electron microscopy.  Inhibitor discovery against both targets is in progress.

References

Strugatsky, D., McNulty, R.M., Munson, K., Chen, C.-K., Soltis, S.M., Sachs, G., Luecke H. "Structure of the proton-gated urea channel from the gastric pathogen Helicobacter pylori" (2013) Nature 493, 255–258.

Luecke, H. & Sachs, G. "Helicobacter pylori’s Achilles' Heel" (2013) Immuno-Gastroenterology 2, 76.

McNulty, R., Ulmschneider, J.P., Luecke, H., Ulmschneider, M.B. "Mechanisms of molecular transport through the urea channel of Helicobacter pylori" (2013) Nature Communications 4, 2900.

Cunha, E.S., Chen, X., Sanz Gaitero, M., Mills, D., Luecke, H. "Cryo EM Structure of Helicobacter pylori inhibitor-bound urease at 2.0 Å resolution." (2021) Nature Communications 12, 230. https://rdcu.be/cdnuc

Brief biography

Hartmut "Hudel" Luecke (born in Göttingen, Germany) is a structural biologist with an emphasis on structure-function studies of membrane proteins and structure-based drug discovery.  He received his B.S. from Heidelberg University, Ohio, with majors in Physics, Chemistry & Computer Science, his Ph.D. from Rice University in 1990 in the area of Macromolecular Crystallography, and performed postdoctoral work with Prof. Robert Huber at the Max-Planck-Institute for Biochemistry in Martinsried.  He began his independent career at the Stanford Synchrotron as a Structural Biologist before joining the faculty at the University of California, Irvine in 1996, where he was a Professor of Biochemistry, Biophysics and Computer Science and as founding director of the UC Irvine Center for Biomembrane Systems.  His work has been published in journals such as Nature (4), Science (4), and Proc. Natl. Acad. Sci. USA (4).  In 2018, Dr. Luecke moved his lab to the Center for Molecular Medicine Norway (NCMM) at the University of Oslo where his group set up cryo electron microscopy facilities to complement their x-ray crystallography efforts.

About ALBA II Colloquium The series ALBA II Colloquium, addressed to the scientific user's community of synchrotron radiation, is aimed at inspiring and promoting fruitful ideas and information exchange about the future development of ALBA II facility.

 

Recording