Specific Binding Sites for Endothelin in the Brain, Spinal Cord, Heart and Kidney

Specific binding sites for potassium, which may be components of the carriers for active transport for K in Chlorella, were characterized by their capacity to bind rubidium. A dense suspension was allowed to take up Rb86 from a low concentration of Rb86 and a high concentration of ions which saturate non-specific sites. The amount bound was derived from the increase in the external concentration of Rb86 following addition of excess potassium. The sites were heterogeneous. The average affinity of Rb and various other ions for the sites was determined by plotting the degree of displacement of Rb86 against log molar concentration of the individual ions. Interpolation gave the concentration for 50 per cent displacement of Rb, which is inversely related to affinity. The order of affinity was not changed when the cells were frozen, or boiled either in water or in 70 per cent ethanol. The affinity is maximal for ions with a crystalline radius of 1.3 to 1.5 A and a high polarizability, and is not related to the hydrated radius or valency. It is suggested that binding groups in a site are rigidly arranged, the irregular space between them being 2.6 to 3.0 A across, so that affinity is high for ions of this diameter and high polarizability.

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Relation of Glucagon-specific Binding Sites to Glucagon-dependent Stimulation of Adenylyl Cyclase Activity in Plasma Membranes of Rat Liver

Journal of Biological Chemistry ◽

10.1016/s0021-9258(19)44186-0 ◽

1973 ◽

Vol 248 (6) ◽

pp. 2056-2061

Author(s):

Lutz Birnbaumer ◽

Stephen L. Pohl

Keyword(s):

Adenylyl Cyclase ◽

Rat Liver ◽

Binding Sites ◽

Plasma Membranes ◽

Specific Binding ◽

Cyclase Activity ◽

Adenylyl Cyclase Activity ◽

Specific Binding Sites ◽

Stimulation Of

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Studies of the uptake of macromolecules by cells. I. Uptake of proteins by cells of the Ehrlich–Lettré ascites carcinoma

Canadian Journal of Biochemistry ◽

10.1139/o68-216 ◽

1968 ◽

Vol 46 (12) ◽

pp. 1443-1450 ◽

Cited By ~ 2

Author(s):

Y. C. Choi ◽

E. R. M. Kay

Keyword(s):

Nucleic Acid ◽

Cell Membrane ◽

Binding Sites ◽

Specific Binding ◽

Protein Uptake ◽

Specific Binding Sites ◽

Model Protein ◽

Uptake Process ◽

Kinetics Of ◽

Protein Treatment

The uptake of protein by cells of the Ehrlich–Lettré ascites carcinoma was characterized kinetically by using hemoglobin as a model protein. An attempt was made to show that the process is not an artefact due to nonspecific adsorption of protein to the cell membrane. The kinetics of the uptake process suggested that an interaction exists between the exogenous protein and specific binding sites on the membrane. Acetylation of hemoglobin enhanced the rate of uptake of this protein. Treatment of cells with neuraminidase, phospholipase A, and Pronase resulted in an inhibition of protein uptake. The experimental evidence for the uptake of hemoglobin was supported by evidence that L-serine-U-14C-labelled hemoglobin is transported into the cytoplasm and utilized subsequently, resulting in labelling of the nucleic acid nucleotides.

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