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dc.contributor.authorNirthanan, Selvanayagam
dc.contributor.authorGarcia, Galo
dc.contributor.authorChiara, David C
dc.contributor.authorHusain, S Shaukat
dc.contributor.authorCohen, Jonathan B
dc.date.accessioned2017-05-03T15:28:59Z
dc.date.available2017-05-03T15:28:59Z
dc.date.issued2008
dc.date.modified2014-10-08T01:43:49Z
dc.identifier.issn0021-9258
dc.identifier.doi10.1074/jbc.M801332200
dc.identifier.urihttp://hdl.handle.net/10072/26747
dc.description.abstractEtomidate, one of the most potent general anesthetics used clinically, acts at micromolar concentrations as an anesthetic and positive allosteric modulator of gamma-aminobutyric acid responses, whereas it inhibits muscle-type nicotinic acetylcholine receptors (nAChRs) at concentrations above 10 microm. We report here that TDBzl-etomidate, a photoreactive etomidate analog, acts as a positive allosteric nAChR modulator rather than an inhibitor, and we identify its binding sites by photoaffinity labeling. TDBzl-etomidate (>10 microm) increased the submaximal response to acetylcholine (10 microm) with a 2.5-fold increase at 60 microm. At higher concentrations, it inhibited the binding of the noncompetitive antagonists [(3)H]tetracaine and [(3)H]phencyclidine to Torpedo nAChR-rich membranes (IC(50) values of 0. 8 mm). nAChR-rich membranes were photolabeled with [(3)H]TDBzl-etomidate, and labeled amino acids were identified by Edman degradation. For nAChRs photolabeled in the absence of agonist (resting state), there was tetracaine-inhibitable photolabeling of amino acids in the ion channel at positions M2-9 (deltaLeu-265) and M2-13 (alphaVal-255 and deltaVal-269), whereas labeling of alphaM2-10 (alphaSer-252) was not inhibited by tetracaine but was enhanced 10-fold by proadifen or phencyclidine. In addition, there was labeling in gammaM3 (gammaMet-299), a residue that contributes to the same pocket in the nAChR structure as alphaM2-10. The pharmacological specificity of labeling of residues, together with their locations in the nAChR structure, indicate that TDBzl-etomidate binds at two distinct sites: one within the lumen of the ion channel (labeling of M2-9 and -13), an inhibitory site, and another at the interface between the alpha and gamma subunits (labeling of alphaM2-10 and gammaMet-299) likely to be a site for positive allosteric modulation.
dc.description.peerreviewedYes
dc.description.publicationstatusYes
dc.format.extent2795529 bytes
dc.format.mimetypeapplication/pdf
dc.languageEnglish
dc.language.isoeng
dc.publisherAmerican Society for Biochemistry and Molecular Biology
dc.publisher.placeBethesda
dc.relation.ispartofstudentpublicationN
dc.relation.ispartofpagefrom22051
dc.relation.ispartofpageto22062
dc.relation.ispartofissue32
dc.relation.ispartofjournalJournal of Biological Chemistry
dc.relation.ispartofvolume283
dc.rights.retentionY
dc.subject.fieldofresearchChemical sciences
dc.subject.fieldofresearchBiological sciences
dc.subject.fieldofresearchBiomedical and clinical sciences
dc.subject.fieldofresearchAnaesthesiology
dc.subject.fieldofresearchCellular nervous system
dc.subject.fieldofresearchcode34
dc.subject.fieldofresearchcode31
dc.subject.fieldofresearchcode32
dc.subject.fieldofresearchcode320201
dc.subject.fieldofresearchcode320902
dc.titleIdentification of binding sites in the nicotinic acetylcholine receptor for TDBzl-etomidate, a photoreactive positive allosteric effector.
dc.typeJournal article
dc.type.descriptionC1 - Articles
dc.type.codeC - Journal Articles
gro.rights.copyrightThis research was originally published in Journal of Biological Chemistry (JBC). Selvanayagam Nirthanan, Galo Garcia III, David C. Chiara, S. Shaukat Husain§, Jonathan B. Cohen, Identification of binding sites in the nicotinic acetylcholine receptor for TDBzl-etomidate, a photoreactive positive allosteric effector Journal of Biological Chemistry (JBC), 2008; 283: 22051-22062. Copyright the American Society for Biochemistry and Molecular Biology. This is the author-manuscript version of this paper. Reproduced in accordance with the copyright policy of the publisher. Please refer to the journal's website for access to the definitve version.
gro.date.issued2008
gro.hasfulltextFull Text
gro.griffith.authorNirthanan, Niru


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