title: Methionine 286 in transmembrane domain 3 of the GABAA receptor beta subunit controls a binding cavity for propofol and other alkylphenol general anesthetics.
abstract: gamma-Aminobutyric acid type A (GABA(A)) receptors are an important target for general anesthetics in the central nervous system. Site-directed mutagenesis techniques have identified amino acid residues that are important for the positive modulation of GABA(A) receptors by general anesthetics. In the present study, we investigate the role of an amino acid residue in transmembrane (TM) domain 3 of the GABA(A) receptor beta(2) subunit for modulation by the general anesthetic 2,6-diisopropylphenol (propofol). Mutation of methionine 286 to tryptophan (M286W) in the beta(2) subunit abolished potentiation of GABA responses by propofol but did not affect direct receptor activation by propofol in the absence of GABA. In contrast, substitution of methionine 286 by alanine, cysteine, glutamate, lysine, phenylalanine, serine, or tyrosine was permissive for potentiation of GABA responses and direct activation by propofol. Using propofol analogs of varying molecular size, we show that the beta(2)(M286W) mutation resulted in a decrease in the 'cut-off' volume for propofol analog molecules to enhance GABA responses at GABA(A) alpha(1)beta(2)gamma(2s) receptors. This suggests that mutation of M286 in the GABA(A) beta(2) subunit alters the dimensions of a 'binding pocket' for propofol and related alkylphenol general anesthetics.
authors.affiliation: Department of Anesthesia and Critical Care, University of Chicago, Chicago, IL 60637, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Krasowski
authors.forename: K
authors.initials: K
authors.lastname: Nishikawa
authors.forename: N
authors.initials: N
authors.lastname: Nikolaeva
authors.forename: A
authors.initials: A
authors.lastname: Lin
authors.forename: N L
authors.initials: NL
authors.lastname: Harrison
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D018681:Anesthetics, General / Q000737:chemistry / Q000378:metabolism*; D018686:Anesthetics, Intravenous / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites / Q000187:drug effects / Q000235:genetics; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D005045:Etomidate / Q000494:pharmacology; D006801:Humans; D008715:Methionine / Q000235:genetics* / Q000494:pharmacology; D008723:Methohexital / Q000494:pharmacology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D015742:Propofol / Q000737:chemistry / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000235:genetics; D051381:Rats; D011963:Receptors, GABA-A / Q000235:genetics / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
chemical_list: D018681:Anesthetics, General; D018686:Anesthetics, Intravenous; D011963:Receptors, GABA-A; D005680:gamma-Aminobutyric Acid; D008715:Methionine; D008723:Methohexital; D015742:Propofol; D005045:Etomidate