A Cholesterol Dimer Stabilizes the Inactivated State of an Inward‐Rectifier Potassium Channel

• Published in: Angewandte Chemie International Edition 2022-03, Vol.61 (13), p.e202112232-n/a
• Main Authors: Borcik, Collin G., Eason, Isaac R., Yekefallah, Maryam, Amani, Reza, Han, Ruixian, Vanderloop, Boden H., Wylie, Benjamin J.
• Format: Article
• Language: English
• Subjects: Cholesterol; Crystal structure; Deactivation; Dimers; Distance measurement; Efflux; Inward-Rectifier K+ Channels; Lipids; Mathematical analysis; Membrane Proteins; Molecular dynamics; NMR; NMR Structure; Nuclear magnetic resonance; Oligomers; Potassium; Potassium - metabolism; Potassium Channels, Inwardly Rectifying - chemistry; Potassium Channels, Inwardly Rectifying - metabolism; Potassium conductance; Protein X; Proteins; Rectifiers; Simulated annealing; Solid-State NMR; Structural analysis; Structure-function relationships
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202112232

Cholesterol oligomers reside in multiple membrane protein X‐ray crystal structures. Yet, there is no direct link between these oligomers and a biological function. Here we present the structural and functional details of a cholesterol dimer that stabilizes the inactivated state of an inward‐rectifier potassium channel KirBac1.1. K+ efflux assays confirm that high cholesterol concentration reduces K+ conductance. We then determine the structure of the cholesterol‐KirBac1.1 complex using Xplor‐NIH simulated annealing calculations driven by solid‐state NMR distance measurements. These calculations identified an α–α cholesterol dimer docked to a cleft formed by adjacent subunits of the homotetrameric protein. We compare these results to coarse grain molecular dynamics simulations. This is one of the first examples of a cholesterol oligomer performing a distinct biological function and structural characterization of a conserved promiscuous lipid binding region. The structure of a cholesterol dimer‐inward rectifier (Kir) channel complex using solid‐state NMR and simulated annealing calculations is solved. The identified cholesterol binding pocket is directly linked to the mechanism of cholesterol‐mediated inactivation of Kir channels. This work is one of the most detailed structural‐functional studies of cholesterol dimer‐protein interactions within a biological membrane.