Journal
JOURNAL OF GENERAL PHYSIOLOGY
Volume 149, Issue 1, Pages 85-103Publisher
ROCKEFELLER UNIV PRESS
DOI: 10.1085/jgp.201611673
Keywords
-
Categories
Funding
- National Institutes of Health [NS-023513, NS-064969]
Ask authors/readers for more resources
Nicotinic acetylcholine receptors are allosteric proteins that generate membrane currents by isomerizing (gating) between resting and active conformations under the influence of neurotransmitters. Here, to explore the mechanisms that link the transmitter-binding sites (TBSs) with the distant gate, we use mutant cycle analyses to measure coupling between residue pairs, phi value analyses to sequence domain rearrangements, and current simulations to reproduce a microsecond shut component (flip) apparent in single-channel recordings. Significant interactions between amino acids separated by >15 angstrom are rare; an exception is between the alpha M2-M3 linkers and the TBSs that are similar to 30 angstrom apart. Linker residues also make significant, local interactions within and between subunits. Phi value analyses indicate that without agonists, the linker is the first region in the protein to reach the gating transition state. Together, the phi pattern and flip component suggest that a complete, resting <-> active allosteric transition involves passage through four brief intermediate states, with brief shut events arising from sojourns in all or a subset. We derive energy landscapes for gating with and without agonists, and propose a structure-based model in which resting -> active starts with spontaneous rearrangements of the M2-M3 linkers and TBSs. These conformational changes stabilize a twisted extracellular domain to promote transmembrane helix tilting, gate dilation, and the formation of a bubble that collapses to initiate ion conduction. The energy landscapes suggest that twisting is the most energetically unfavorable step in the resting -> active conformational change and that the rate-limiting step in the reverse process is bubble formation.
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