Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 115, Issue 52, Pages E12172-E12181Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1813378116
Keywords
pentameric ligand-gated ion channel; pH activation; proton sensor; electrostatic networks; allosteric modulation
Categories
Funding
- German Research Foundation [SFB 1078]
- Agence Nationale de la Recherche [ANR-13-BSV-8]
- Chinese Scholarship Council
- Institut Pasteur
Ask authors/readers for more resources
The pentameric ligand-gated ion channel (pLGIC) from Gloeo-bacter violaceus (GLIC) has provided insightful structure-function views on the permeation process and the allosteric regulation of the pLGICs family. However, GLIC is activated by pH instead of a neurotransmitter and a clear picture for the gating transition driven by protons is still lacking. We used an electrostatics-based (finite difference Poisson-Boltzmann/Debye-Huckel) method to predict the acidities of all aspartic and glutamic residues in GLIC, both in its active and closed-channel states. Those residues with a predicted pKa close to the experimental pH50 were individually replaced by alanine and the resulting variant receptors were titrated by ATR/FTIR spectroscopy. E35, located in front of loop F far away from the orthosteric site, appears as the key proton sensor with a measured individual pKa at 5.8. In the GLIC open conformation, E35 is connected through a water-mediated hydrogen-bond network first to the highly conserved electrostatic triad R192D122-D32 and then to Y197-Y119-K248, both located at the extracellular domain-transmembrane domain interface. The second triad controls a cluster of hydrophobic side chains from the M2-M3 loop that is remodeled during the gating transition. We solved 12 crystal structures of GLIC mutants, 6 of them being trapped in an agonist-bound but nonconductive conformation. Combined with previous data, this reveals two branches of a continuous network originating from E35 that reach, independently, the middle transmembrane region of two adjacent subunits. We conclude that GLIC's gating proceeds by making use of loop F, already known as an allosteric site in other pLGICs, instead of the classic orthosteric site.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available