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951.
D. S. Coffman Ben H. Leichtling H. V. Rickenberg 《Journal of cellular biochemistry》1981,15(4):369-385
The phosphoproteins of Dictyostelium discoideum were compared at different stages of development by polyacrylamide gel electrophoresis. Certain phosphoproteins of vegetative amoebae were conserved while others appeared and disappeared during development. Four major phosphoproteins with apparent subunit molecular weights of 50,000, 47,000, 38,000, and 34,000 disappeared precociously in response to exogenous cAMP. Two membranal phosphoproteins, with apparent subunit molecular weights of 80,000 and 81,000, appeared precociously in response to added cAMP. One of these phosphoproteins, molecular weight of 80,000, has been identified tentatively as the “contact site A” glycoprotein. Another membranal protein, with apparent subunit molecular weight of 42,000, unaffected in its appearance by cAMP, has been identified tentatively as phosphoactin. 相似文献
952.
953.
THE EXPERIMENTAL STUDY OF VEGETATION 总被引:4,自引:3,他引:1
C. D. PIGOTT 《The New phytologist》1982,90(3):389-404
954.
We have found that the binding of pyridoxal-5′-phosphate to 6 primary amino groups leads to the inactivation of the enzyme. A preferential reaction of pyridoxal-5′-phosphate with the α-subunits of this enzyme can be demonstrated. The reactivity of the amino groups is influenced by various effectors. In the presence of ATP the inhibition of the ATPase activity is noncompetitive. 相似文献
955.
956.
957.
Two methods were used to radioiodinate sea urchin sperm: lactoperoxidase-glucose oxidase and Iodo-Gen. Following iodination the sperm are viable, they undergo the acrosome reaction, and they fertilize eggs. Of the radioactivity associated with the labeled sperm, 28–50% is presumed to be free 125I?, 37–47% is incorporated in lipid, and 8–15% is in trypsin-digestible material believed to be protein. Digestion of the labeled, living sperm with trypsin removes 95.6–99.5% of the macromolecular label (the cells are alive after digestion) suggesting that almost all the protein label is on the external surface of the cell. Thin-layer chromatography of the lipid fraction shows that the major membrane phospholipids and cholesterol are labeled. SDS-PAGE analysis shows the protein-incorporated 125I is distributed among four glycoproteins of >250K, 84K, 64K, and 52K dalton apparent molecular weight. Twenty-eight percent of the total protein (trypsin-digestible) label is in the 84K component and 46% in the 64K band. Although both molecules contain much of the label, they are relatively minor components of the TX-100 extract of sperm. The methods outlined will be useful in determining the role of sperm surface components in fertilization. 相似文献
958.
959.
In this paper the investigation results of successional processes in the vegetative cover appearing due to succession starting
in native ecosystem inundation zone under Sayan-Shush reservoir influence are given. 相似文献
960.
Molecular alteration of a muscarinic acetylcholine receptor system during synaptogenesis 总被引:7,自引:0,他引:7
T H Large N J Cho F G De Mello W L Klein 《The Journal of biological chemistry》1985,260(15):8873-8881
Biochemical properties of the muscarinic acetylcholine receptor system of the avian retina were found to change during the period when synapses form in ovo. Comparison of ligand binding to membranes obtained before and after synaptogenesis showed a significant increase in the affinity, but not proportion, of the high affinity agonist-binding state. There was no change in receptor sensitivity to antagonists during this period. Pirenzepine binding, which can discriminate muscarinic receptor subtypes, showed the presence of a single population of low affinity sites (M2) before and after synaptogenesis. The change in agonist binding was not due to the late development of receptor function; tests for receptor-stimulated phosphatidylinositol turnover and for modulation of agonist binding by guanylylimidodiphosphate showed functional coupling to be present several days prior to the onset of synapse formation. However, detergent-solubilization of membranes eliminated differences in agonist binding between receptors from embryos and hatched chicks, suggesting a developmental change in interactions of the receptor with functionally related membrane components. A possible basis for altered interactions was obtained from isoelectric point data showing that the muscarinic receptor population underwent a transition from a predominantly low pI form (4.25) in 13 day embryos to a predominantly high pI form (4.50) in newly hatched chicks. The possibility that biochemical changes in the muscarinic receptor play a role in differentiation of the system by controlling receptor position on the surface of nerve cells is discussed. 相似文献