title: An alcohol-sensing site in the calcium- and voltage-gated, large conductance potassium (BK) channel.
abstract: Ethanol alters BK (slo1) channel function leading to perturbation of physiology and behavior. Site(s) and mechanism(s) of ethanol-BK channel interaction are unknown. We demonstrate that ethanol docks onto a water-accessible site that is strategically positioned between the slo1 calcium-sensors and gate. Ethanol only accesses this site in presence of calcium, the BK channel's physiological agonist. Within the site, ethanol hydrogen-bonds with K361. Moreover, substitutions that hamper hydrogen bond formation or prevent ethanol from accessing K361 abolish alcohol action without altering basal channel function. Alcohol interacting site dimensions are approximately 10.7 × 8.6 × 7.1 Å, accommodating effective (ethanol-heptanol) but not ineffective (octanol, nonanol) channel activators. This study presents: (i) to our knowledge, the first identification and characterization of an n-alkanol recognition site in a member of the voltage-gated TM6 channel superfamily; (ii) structural insights on ethanol allosteric interactions with ligand-gated ion channels; and (iii) a first step for designing agents that antagonize BK channel-mediated alcohol actions without perturbing basal channel function.
authors.affiliation: Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN 38163.
authors.forename: Anna N
authors.initials: AN
authors.lastname: Bukiya
authors.affiliation: Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN 38163.
authors.forename: Guruprasad
authors.initials: G
authors.lastname: Kuntamallappanavar
authors.affiliation: Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN 38163.
authors.forename: Justin
authors.initials: J
authors.lastname: Edwards
authors.affiliation: Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN 38163.
authors.forename: Aditya K
authors.initials: AK
authors.lastname: Singh
authors.affiliation: Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN 38163.
authors.forename: Bangalore
authors.initials: B
authors.lastname: Shivakumar
authors.affiliation: Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN 38163 adopico@uthsc.edu.
authors.forename: Alex M
authors.initials: AM
authors.lastname: Dopico
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D002492:Central Nervous System Depressants / Q000737:chemistry* / Q000494:pharmacology; D000431:Ethanol / Q000737:chemistry* / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D051379:Mice; D020125:Mutation, Missense; D013329:Structure-Activity Relationship
chemical_list: D002492:Central Nervous System Depressants; C465449:Kcnma1 protein, mouse; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D000431:Ethanol; D002118:Calcium
keywords: MaxiK channel; calcium sensitivity; ethanol site; patch-clamp electrophysiology; potassium channel