3 resultados para aggregation rules

em WestminsterResearch - UK


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Opposition is rarely a good preparation for government. The only post‐war government to enter office confident, well‐acquainted with the Civil Service and with a fund of administrative experience to draw on was the Attlee administration formed in 1945. The longer a party spends in opposition the more these assets disappear. Labour, by the end of the long period of Conservative rule in 1951–64, was largely unfamiliar with the burdens of office. This formed the background to the formulation of the Douglas‐Home rules, whereby informal contact is permitted between the Civil Service and the Opposition in advance of a general election. Since 1964 this arrangement has gradually become more extensive (especially after Neil Kinnock complained that the period for contact was too brief during the run‐up to the 1992 election) and more formalised. In late 1993 John Major agreed that contacts could be made from early 1996 in advance of the next election, rather than only during the last six months of a parliament, as had by then become the convention.’ The object of this short paper is, however, to explain how these rules originated.

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AMPA receptors are glutamate-gated cation channels assembled from GluA1-4 subunits and have properties that are strongly dependent on the subunit composition. The subunits have different propensities to form homomeric or various heteromeric receptors expressed on cell surface, but the underlying mechanisms are still poorly understood. Here, we examined the biochemical basis for the poor ability of GluA3 subunits to form homomeric receptors, linked previously to two amino acid residues, Y454 and R461, in its ligand-binding domain (LBD). Surface expression of GluA3 was improved by co-assembly with GluA2 but not with stargazin, a trafficking chaperone and modulator of AMPA receptors. The secretion efficiency of GluA2 and GluA3 LBDs paralleled the transport difference between the respective full-length receptors and was similarly dependent on Y454/R461, but not on LBD stability. In comparison to GluA2, GluA3 homomeric receptors showed a strong and Y454/R461-dependent tendency to aggregate both in the macroscopic scale measured as lower solubility in nonionic detergent and in the microscopic scale evident as the preponderance of hydrodynamically large structures in density gradient centrifugation and native gel electrophoresis. We conclude that the impaired surface expression of homomeric GluA3 receptors is caused by nonproductive assembly and aggregation to which LBD residues Y454 and R461 strongly contribute. This aggregation inhibits the entry of newly synthesized GluA3 receptors to the secretory pathway.