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  • 1
    Electronic Resource
    Electronic Resource
    Muscarinic Acetylcholine Receptors from Avian Retina and Heart Undergo Different Patterns of Molecular Maturation (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 50 (1988), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Muscarinic acetylcholine receptors (mAChRs) from the avian CNS exist in two molecular weight forms whose concentrations change during development. Here, we have compared the development of mAChRs from embryonic hearts with those of the CNS. Analysis of [3H]-propylbenzilylcholine mustard (PrBCM)-labeled retina and heart mAChRs by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed two atropine-sensitive peaks for each tissue. Apparent molecular masses of retina mAChRs, 86 ± 0.7 kilodaltons (kDa) and 72 ± 0.7 kDa, were different from those of heart mAChRs, 77 ± 1.0 kDa and 52 ± 0.9 kDa. During retina development, the major receptor type changed from 86 kDa to 72 kDa. No such change occurred during heart development. Furthermore, the 52-kDa species appeared to be generated by endogenous proteolysis, as prolonged incubation of heart membranes at 37°C increased the amount of 52-kDa peptide with a decrease of 77-kDa peptide. Protease inhibitors blocked this conversion. Incubation of retina membranes at 37°C did not result in a conversion of the 86-kDa peptide into the 72-kDa peptide, but it did cause the appearance of a minor amount of 52-kDa peptide. The proteolysis of retina mAChRs was not enhanced by cohomogenizing them with heart tissue, arguing against the presence of releasable proteases in heart. Membrane-bound retina and heart mAChRs displayed similar sensitivity to exogenous (Staphylococcus aureus V8) protease, indicating that heart receptors were not unusually susceptible to proteolytic attack; analysis of the labeled polypeptides with the V8 protease showed different patterns of digestion for the retina and heart receptors. Chronic treatment of embryos with a muscarinic agonist reduced the concentration of receptors, but the Mr profile remained unaffected. The fact that muscle mAChRs, unlike neural mAChRs, do not change molecular forms during development may reflect different mechanisms of synaptogenesis in CNS and PNS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1988.tb03023.x
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  • 2
    Electronic Resource
    Electronic Resource
    Glycoprotein Properties of Muscarinic Acetylcholine Receptors from Bovine Cerebral Cortex (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 46 (1986), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Muscarinic acetylcholine receptors from bovine cerebral cortex were solubilized in digitonin for the subsequent determination of several biochemical properties. The digitonin-solubilized receptors were representative of the entire membrane-bound population of muscarinic receptors with respect to carbohydrate content, isoelectric point, and molecular weight. The glycoprotein nature of the solubilized receptors was demonstrated by their quantitative binding to wheat germ agglutinin-aga-rose. The presence of a bound antagonist did not decrease the extent of receptor binding to this lectin. Treatment of receptors with neuraminidase to remove N-acetylneuraminic acid residues reduced binding to wheat germ agglutinin-agarose by 40%; further treatment with endo-glycosidases D and H, to remove all N-linked carbohydrate, decreased binding by a total of 67%. Removal of N-acetylneuraminic acid residues had no effect on agonist binding properties of the membrane-bound receptors. The carbohydrate-specific enzymes were further used to assess the contribution of carbohydrate to the isoelectric point and molecular weight of the receptor. Muscarinic receptors solubilized in either digitonin or Triton X-100 focused as one major species with a pI of 4.3. Neuraminidase treatment resulted in an increase of 0.17 units in the pi of the receptor. Muscarinic receptors labeled with the covalent muscarinic antagonist propylbenzilylcholine mustard migrated as a single major polypeptide with a molecular weight of 73,000 on sodium dodecyl sulfate-urea-polyacrylamide gels. The exclusion of urea from these gels severely retarded receptor mobility, indicating a strong tendency for aggregation of receptors in SDS. Removal of N-linked carbohydrate by endoglycosidase treatment reduced the molecular weight of the antagonist binding polypeptide by no more than 5%. These results demonstrate the glycoprotein nature of muscarinic receptors from mammalian cerebral cortex and provide evidence for their heterogeneity with respect to carbohydrate content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1986.tb12920.x
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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