Evidence for the presence of specific binding sites for corticoids in mouse liver plasma membranes

In the present study we describe the characterization and localization of Ins(1,3,4,5)P4-binding sites in human platelet membranes. Specific binding sites for Ins(1,3,4,5)P4 have been identified on mixed, plasma and intracellular membranes from neuraminidase-treated platelets using highly purified carrier-free [32P]Ins(1,3,4,5)P4. The displacement of Ins(1,3,4,5)P4 from these sites by Ins(1,4,5)P3 and InsP6 occurs at greater than two orders of magnitude higher concentrations and with Ins(1,3,4,5,6)P5 at about 40-fold higher concentrations than with Ins(1,3,4,5)P4. The membranes were further separated by free-flow electrophoresis into plasma and intracellular membranes. The Ins(1,3,4,5)P4-binding sites separated with plasma membranes, and showed similar affinities and specificities as mixed membranes, whereas Ins(1,4,5)P3-binding sites were predominantly in the intracellular membranes. These results suggest a predominantly plasma membrane location for putative Ins(1,3,4,5)P4 receptors in human platelets.

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Comparative studies on fish and bird insulin receptors.

Acta Biochimica Polonica ◽

10.18388/abp.1993_4823 ◽

1993 ◽

Vol 40 (2) ◽

pp. 231-236

Author(s):

K W Nowak ◽

P Maćkowiak ◽

L Nogowski

Keyword(s):

Binding Affinity ◽

Comparative Studies ◽

Binding Sites ◽

Plasma Membranes ◽

Species Differences ◽

Specific Binding ◽

Insulin Receptors ◽

Binding Ability ◽

Liver Plasma Membranes ◽

Scatchard Plots

The comparative studies were performed on insulin receptors of erythrocytes and liver plasma membranes in fish (tench and carp) and bird (duck). The Scatchard plots indicated the presence of two pools of binding sites both in fish and duck. These pools show inter-species differences in binding ability and the number of receptors. Specific binding of insulin and the binding affinity are higher in duck than in fish.

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Contribution of gangliosides to thyroxin binding with plasma membranes

Problems of Endocrinology ◽

10.14341/probl11370 ◽

1995 ◽

Vol 41 (2) ◽

pp. 28-30

Author(s):

T. S. Saatov ◽

F. Ya. Gulyamova ◽

G. U. Usmanova

Keyword(s):

Binding Sites ◽

Plasma Membranes ◽

Binding Capacity ◽

Specific Binding ◽

Brain Cell ◽

Cell Recognition ◽

High Affinity ◽

Specific Binding Sites

Besides intracellular receptors of thyroid hormones, specific binding sites for T3 and T4 were detected on plasma membranes (PM) of some cells and a relationship between membrane reception .and lipid composition of membranes shown. The parameters of 125I-T4 binding to highly purified PM of hepatic and cerebral cells of rats were studied. The hepatic and cerebral cellular membranes were found to contain two sites of hormone binding each, one of these sites being characterized by a high affinity and low capacity, and the other by low affinity and a higher binding capacity. The association constant of highly affine site of hepatocyte membranes was found to be higher than that of brain cell membranes. T4 membranous receptors may be significant in the process of cell “recognition" by the hormone. In vivo and in vitro experiments with 125I-T4 and 14C-labeled thyroxin in ganglioside fractions showed appreciable binding of the hormone to Gm3 fraction, this evidently pointing to participation of this, ganglioside in T4 interaction with membrane receptor. It is possible that gangliosides situated on membranous surface are components of or function as receptors.

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