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Biochemistry (Easton), 2003-04, Vol.42 (14), p.4197-4207
2003
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Details

Autor(en) / Beteiligte
Titel
Site-Selective Agonist Binding to the Nicotinic Acetylcholine Receptor from Torpedo californica
Ist Teil von
  • Biochemistry (Easton), 2003-04, Vol.42 (14), p.4197-4207
Ort / Verlag
United States: American Chemical Society
Erscheinungsjahr
2003
Quelle
MEDLINE
Beschreibungen/Notizen
  • Fluorescent energy transfer measurements of dansyl-C6-choline binding to the nicotinic acetylcholine receptor (AChR) from Torpedo californica were used to determine binding characteristics of the αγ and αδ binding sites. Equilibrium binding measurements show that the αγ site has a lower fluorescence than the αδ site; the emission difference is due to differences in the intrinsic fluorescence of the bound fluorophores rather than differences in energy transfer at the two sites. Stopped-flow fluorescence kinetics showed that dissociation of dansyl-C6-choline from the AChR in the desensitized conformation occurs 5−10-fold faster from the αγ site than from the αδ site. The dissociation rates are robust for distinct protein preparations, in the presence of noncompetitive antagonists, and over a broad range of ionic strengths. Equilibrium fluorescent binding measurements show that dansyl-C6-choline binds with higher affinity to the αδ site (K = 3 nM) than to the αγ site (K = 9 nM) when the AChR is desensitized. Similar affinity differences were observed for acetylcholine itself. The distinct dissociation rates permit the extent of desensitization to be measured at each site during the time course of binding. This sequential mixing method of measuring the desensitized state population at each agonist site can be applied to study the mechanism of AChR activation and subsequent desensitization in detail.
Sprache
Englisch
Identifikatoren
ISSN: 0006-2960
eISSN: 1520-4995
DOI: 10.1021/bi027405b
Titel-ID: cdi_proquest_miscellaneous_73181325

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