@article {2022|2160,
	title = {Open-channel structure of a pentameric ligand-gated ion channel reveals a mechanism of leaflet-specific phospholipid modulation},
	journal = {Nature Communications},
	volume = {13},
	year = {2022},
	doi = {10.1038/s41467-022-34813-5},
	url = {https://doi.org/10.1038/s41467-022-34813-5},
	author = {John T. Petroff and Noah M. Dietzen and Ezry Santiago-McRae and Brett Deng and Maya S. Washington and Lawrence J. Chen and K. Trent Moreland and Zengqin Deng and Michael Rau and James A. J. Fitzpatrick and Peng Yuan and Thomas T. Joseph and J{\'e}r{\^o}me H{\'e}nin and Grace Brannigan and Wayland W. L. Cheng}
}
@article {2016|1672,
	title = {A Novel Bifunctional Alkylphenol Anesthetic Allows Characterization of gamma-Aminobutyric Acid, Type A (GABAA), Receptor Subunit Binding Selectivity in Synaptosomes.},
	journal = {J. Biol. Chem},
	volume = {291},
	year = {2016},
	month = {sep},
	pages = {20473{\textendash}86},
	abstract = {<p>Propofol, an intravenous anesthetic, is a positive modulator of the GABAA receptor, but the mechanistic details, including the relevant binding sites and alternative targets, remain disputed. Here we undertook an in-depth study of alkylphenol-based anesthetic binding to synaptic membranes. We designed, synthesized, and characterized a chemically active alkylphenol anesthetic (2-((prop-2-yn-1-yloxy)methyl)-5-(3-(trifluoromethyl)-3H-diazirin-3-yl)phenol, AziPm-click (1)), for affinity-based protein profiling (ABPP) of propofol-binding proteins in their native state within mouse synaptosomes. The ABPP strategy captured approximately 4\% of the synaptosomal proteome, including the unbiased capture of five alpha or beta GABAA receptor subunits. Lack of gamma2 subunit capture was not due to low abundance. Consistent with this, independent molecular dynamics simulations with alchemical free energy perturbation calculations predicted selective propofol binding to interfacial sites, with higher affinities for alpha/beta than gamma-containing interfaces. The simulations indicated hydrogen bonding is a key component leading to propofol-selective binding within GABAA receptor subunit interfaces, with stable hydrogen bonds observed between propofol and alpha/beta cavity residues but not gamma cavity residues. We confirmed this by introducing a hydrogen bond-null propofol analogue as a protecting ligand for targeted-ABPP and observed a lack of GABAA receptor subunit protection. This investigation demonstrates striking interfacial GABAA receptor subunit selectivity in the native milieu, suggesting that asymmetric occupancy of heteropentameric ion channels by alkylphenol-based anesthetics is sufficient to induce modulation of activity.</p>},
	keywords = {anesthesia, anesthetic, click chemistry, GABA receptor, photoaffinity labeling},
	doi = {10.1074/jbc.M116.736975},
	author = {Woll, Kellie A. and Murlidaran, Sruthi and Pinch, Benika J. and J{\'e}r{\^o}me H{\'e}nin and Wang, Xiaoshi and Salari, Reza and Covarrubias, Manuel and Dailey, William P. and Grace Brannigan and Garcia, Benjamin A. and Roderic G Eckenhoff}
}
@article {2015|1664,
	title = {Membrane Protein Structure, Function, and Dynamics: a Perspective from Experiments and Theory.},
	journal = {J. Membr. Biol.},
	volume = {248},
	year = {2015},
	publisher = {Biomedical Research Foundation, Academy of Athens, 4 Soranou Ephessiou, 11527, Athens, Greece, zcournia@bioacademy.gr.},
	chapter = {611},
	abstract = {<p>Membrane proteins mediate processes that are fundamental for the flourishing of biological cells. Membrane-embedded transporters move ions and larger solutes across membranes; receptors mediate communication between the cell and its environment and membrane-embedded enzymes catalyze chemical reactions. Understanding these mechanisms of action requires knowledge of how the proteins couple to their fluid, hydrated lipid membrane environment. We present here current studies in computational and experimental membrane protein biophysics, and show how they address outstanding challenges in understanding the complex environmental effects on the structure, function, and dynamics of membrane proteins.</p>},
	doi = {10.1007/s00232-015-9802-0},
	author = {Cournia, Zoe and Allen, Toby W. and Andricioaei, Ioan and Antonny, Bruno and Baum, Daniel and Grace Brannigan and Buchete, Nicolae-Viorel and Deckman, Jason T. and Delemotte, Lucie and Del Val, Coral and Friedman, Ran and Gkeka, Paraskevi and Hege, Hans-Christian and J{\'e}r{\^o}me H{\'e}nin and Kasimova, Marina A. and Kolocouris, Antonios and Michael L Klein and Khalid, Syma and Lemieux, M Joanne and Lindow, Norbert and Roy, Mahua and Selent, Jana and Mounir Tarek and Tofoleanu, Florentina and Vanni, Stefano and Urban, Sinisa and Wales, David J. and Smith, Jeremy C. and Bondar, Ana-Nicoleta}
}
@article {2014|1598,
	title = {A predicted binding site for cholesterol on the GABAA receptor.},
	journal = {Biophys. J.},
	volume = {106},
	number = {9},
	year = {2014},
	month = {may},
	pages = {1938{\textendash}1949},
	publisher = {Department of Physics, Rutgers University-Camden, Camden, New Jersey; Center for Computational and Integrative Biology, Rutgers University-Camden, Camden, New Jersey. Electronic address: Grace.Brannigan@rutgers.edu.},
	abstract = {Modulation of the GABA type A receptor (GABAAR) function by cholesterol and other steroids is documented at the functional level, yet its structural basis is largely unknown. Current data on structurally related modulators suggest that cholesterol binds to subunit interfaces between transmembrane domains of the GABAAR. We construct homology models of a human GABAAR based on the structure of the glutamate-gated chloride channel GluCl of Caenorhabditis elegans. The models show the possibility of previously unreported disulfide bridges linking the M1 and M3 transmembrane helices in the α and γ subunits. We discuss the biological relevance of such disulfide bridges. Using our models, we investigate cholesterol binding to intersubunit cavities of the GABAAR transmembrane domain. We find that very similar binding modes are predicted independently by three approaches: analogy with ivermectin in the GluCl crystal structure, automated docking by AutoDock, and spontaneous rebinding events in unbiased molecular dynamics simulations. Taken together, the models and atomistic simulations suggest a somewhat flexible binding mode, with several possible orientations. Finally, we explore the possibility that cholesterol promotes pore opening through a wedge mechanism.},
	keywords = {Amino Acid, Binding Sites, Caenorhabditis elegans Proteins, chemistry, chemistry/metabolism, Chloride Channels, Cholesterol, GABA-A, Humans, Hydrogen Bonding, Ivermectin, metabolism, Molecular Docking Simulation, Molecular Dynamics Simulation, Porosity, Protein Binding, Protein Conformation, Receptors, Sequence Homology, Substrate Specificity},
	doi = {10.1016/j.bpj.2014.03.024},
	author = {J{\'e}r{\^o}me H{\'e}nin and Salari, Reza and Murlidaran, Sruthi and Grace Brannigan}
}
@article {2010|1865,
	title = {An atomistic model for simulations of the general anesthetic isoflurane},
	journal = {J. Phys. Chem. B},
	volume = {114},
	number = {1},
	year = {2010},
	pages = {604{\textendash}612},
	publisher = {Laboratoire d{\textquoteright}Ing{\'e}nierie des Syst{\`e}mes Macromol{\'e}culaires, CNRS, Marseille, France. jhenin@ifr88.cnrs-mrs.fr},
	abstract = {An atomistic model of isoflurane is constructed and calibrated to describe its conformational preferences and intermolecular interactions. The model, which is compatible with the CHARMM force field for biomolecules, is based on target quantities including bulk liquid properties, molecular conformations, and local interactions with isolated water molecules. Reference data is obtained from tabulated thermodynamic properties and high-resolution structural information from gas-phase electron diffraction, as well as DFT calculations at the B3LYP level. The model is tested against experimentally known solvation properties in water and oil, and shows quantitative agreement. In particular, isoflurane is faithfully described as lipophilic, yet nonhydrophobic, a combination of properties critical to its pharmacological activity. Intermolecular interactions of the model are further probed through simulations of the binding of isoflurane to a binding site in horse spleen apoferritin (HSAF). The observed binding mode compares well with crystallographic data, and the calculated binding affinities are compatible with experimental results, although both computational and experimental measurements are challenging and provide results with limited precision. The model is expected to be useful for detailed simulations of the elementary molecular processes associated with anesthesia. Full parameters are provided as Supporting Information.},
	doi = {10.1021/jp9088035},
	author = {J{\'e}r{\^o}me H{\'e}nin and Grace Brannigan and William P Dailey and Roderic G Eckenhoff and Michael L Klein}
}
@article {2010|1971,
	title = {Multiple binding sites for the general anesthetic isoflurane identified in the nicotinic acetylcholine receptor transmembrane domain.},
	journal = {Proc. Natl. Acad. Sci. U.s.a.},
	volume = {107},
	number = {32},
	year = {2010},
	pages = {14122{\textendash}14127},
	abstract = {An extensive search for isoflurane binding sites in the nicotinic acetylcholine receptor (nAChR) and the proton gated ion channel from Gloebacter violaceus (GLIC) has been carried out based on molecular dynamics (MD) simulations in fully hydrated lipid membrane environments. Isoflurane introduced into the aqueous phase readily partitions into the lipid membrane and the membrane-bound protein. Specifically, isoflurane binds persistently to three classes of sites in the nAChR transmembrane domain: (i) An isoflurane dimer occludes the pore, contacting residues identified by previous mutagenesis studies; analogous behavior is observed in GLIC. (ii) Several nAChR subunit interfaces are also occupied, in a site suggested by photoaffinity labeling and thought to positively modulate the receptor; these sites are not occupied in GLIC. (iii) Isoflurane binds to the subunit centers of both nAChR alpha chains and one of the GLIC chains, in a site that has had little experimental targeting. Interpreted in the context of existing structural and physiological data, the present MD results support a multisite model for the mechanism of receptor-channel modulation by anesthetics.},
	doi = {10.1073/pnas.1008534107},
	author = {Grace Brannigan and David N LeBard and J{\'e}r{\^o}me H{\'e}nin and Roderic G Eckenhoff and Michael L Klein}
}
@article {2008|1970,
	title = {Embedded cholesterol in the nicotinic acetylcholine receptor},
	journal = {Proc. Natl. Acad. Sci. U.s.a.},
	volume = {105},
	number = {38},
	year = {2008},
	pages = {14418{\textendash}14423},
	publisher = {Center for Molecular Modeling, Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA. grace@cmm.upenn.edu},
	abstract = {The nicotinic acetylcholine receptor (nAChR) is a cation-selective channel central to both neuronal and muscular processes and is considered the prototype for ligand-gated ion channels, motivating a structural determination effort that spanned several decades [Unwin N (2005) Refined structure of the nicotinic acetylcholine receptor at 4 A resolution. J Mol Biol 346:967-989]. Purified nAChR must be reconstituted in a mixture containing cholesterol to function. Proposed modes of interaction between cholesterol and the protein range from specific binding to indirect membrane-mediated mechanisms. However, the underlying cause of nAChR sensitivity to cholesterol remains controversial, in part because the vast majority of functional studies were conducted before a medium resolution structure was reported. We show that the nAChR contains internal sites capable of containing cholesterol, whose occupation stabilizes the protein structure. We detect sites at the protein-lipid interface as conventionally predicted from functional data, as well as deeply buried sites that are not usually considered. Molecular dynamics simulations reveal that occupation of both superficial and deeply buried sites most effectively preserves the experimental structure; the structure collapses in the absence of bound cholesterol. In particular, we find that bound cholesterol directly supports contacts between the agonist-binding domain and the pore that are thought to be essential for activation of the receptor. These results likely apply to those other ion channels within the Cys-loop superfamily that depend on cholesterol, such as the GABA receptor.},
	doi = {10.1073/pnas.0803029105},
	author = {Grace Brannigan and J{\'e}r{\^o}me H{\'e}nin and Richard Law and Roderic G Eckenhoff and Michael L Klein}
}
