Characterisation of an allosteric modulatory protein associated with alpha-[3H]amino-3-hydroxy-5-methylisoxazolepropionate binding sites in chick telencephalon: effects of high-energy radiation and detergent solubilisation.

Article date: 1992/6/1

PubMed ID: 1374116

Journal name: Journal of neurochemistry (ISSN: 0022-3042)


alpha-[3H]Amino-3-hydroxy-5-methylisoxazolepropionate ([3H]AMPA) binds to 1-day-old chick telencephalon membranes with KD and Bmax values of 138 nM and 2.56 pmol/mg of protein, respectively. High-energy radiation bombardment of intact frozen telencephalon resulted in a biphasic inactivation curve for [3H]AMPA binding. At a 5.8-Mrad radiation dose, the affinity of [3H]AMPA binding was increased (54 nM), but there was no apparent alteration in the Bmax value (2.76 pmol/mg of protein). We attribute this phenomenon to the inactivation of a high molecular weight modulatory protein that down-regulates the affinity of [3H]AMPA binding. The estimated molecular masses of the AMPA binding site and of the modulatory component were 59 and 108 kDa, respectively. Solubilisation with n-octyl-beta-glucopyranoside resulted in an increase in the Bmax (4.7 pmol/mg of protein) with no pronounced alteration in the affinity (109 nM) of [3H]AMPA binding. However, the solubilisation-induced increase in Bmax did not occur in telencephalon irradiated before solubilisation. In contrast, the increase in affinity induced by radiation treatment was still detected in solubilised extracts. These results suggest that the number and affinity of [3H]AMPA sites in chick telencephalon are closely regulated and that the modulatory systems involved are affected by both irradiation and solubilisation.

Author List: Henley J M, Nielsen M, Barnard E A

Publication Types: Journal Article

Substances mentioned in the article: Glucosides; Tritium; Ibotenic Acid; octyl-beta-D-glucoside; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid;

Mesh terms: Allosteric Regulation/drug effects; Animals; Binding Sites/drug effects; Centrifugation, Density Gradient; Chickens; Dose-Response Relationship, Radiation; Glucosides/pharmacology; Ibotenic Acid/analogs & derivatives; Telencephalon/drug effects; Tritium; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid;

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