Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.5 (5'-nucleotidase)
 3,167 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

High density lipoprotein (HDL) stimulates excretion of excess intracellular cholesterol from cells, presumably by interacting with a cell-surface receptor. A 110 kDa membrane protein that is a candidate for the HDL receptor has been identified by ligand blot analysis. In this study we determined the cellular localization of this and other HDL-binding proteins and characterized their properties. The plasma membranes (PM) of cultured bovine aortic endothelial cells were labeled with trace amounts of [3H]cholesterol, and cell homogenates were fractionated on sucrose and Percoll gradients. Ligand blot analysis of homogenates of cultured bovine aortic endothelial cells demonstrated that cells contain multiple proteins that bind HDL3, including a major membrane protein with an apparent M(r) of 110 kDa and two minor ones with M(r) of 105 and 130 kDa. The gradient distribution of the 105, 110, and 130 kDa HDL-binding proteins mirrored that of labeled cholesterol and 5'-nucleotidase, both PM markers. Treatment of intact cells with the water-soluble cross-linker bis(sulfosuccinimidyl)suberate abolished the HDL binding activity of the 110 and 130 kDa proteins but not that of the 105 kDa protein. These findings suggest that the 105, 110, and 130 kDa HDL-binding proteins are localized to the PM and that at least two of these proteins are exposed to the extracellular fluid. Solubilized 110 and 130 kDa proteins were retained on wheat-germ agglutinin and abrin lectin columns, showing that they are glycoproteins. The cellular localization and physical properties of the 110 and 130 kDa proteins suggest that they may play a role in binding of HDL to the cell surface.
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PMID:Cellular localization and characterization of proteins that bind high density lipoprotein. 132 47

The binding of human 125I-labeled HDL3 to purified rat liver and testis plasma membranes was studied. About 50-65% of the total HDL binding in these membranes was abolished by 1% bovine serum albumin in the incubation medium. The remaining albumin-insensitive binding sites, determined in the presence of albumin were associated with plasma membranes; a good correlation was found between the 125I-labeled HDL3 binding and the 5'-nucleotidase activities of the membrane fractions. The binding sites in these tissues were saturable, specific for HDL (not competed for by LDL) and had similar affinities for 125I-labeled HDL3 (Kd, 11.8 micrograms protein/ml for liver and 12.7 micrograms protein/ml for testis membranes); the maximum binding capacity of the testis membranes was higher (1.3 vs. 0.7 microgram protein/mg membrane protein). Egg phosphatidylcholine complexes of both human apolipoprotein A-I and apolipoprotein C's competed for the HDL-binding sites, but phosphatidylcholine vesicles alone did not. Chemical modification of the lysine and arginine residues of apolipoproteins did not affect the interaction of HDL3 with its binding sites. Despite the fact that the HDL-binding sites in these tissues are not specific for apolipoprotein A-I, they may have important physiological roles in lipid transport, as they appear to recognize apolipoprotein-phospholipid complexes.
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PMID:Characterization of high-density lipoprotein binding sites in rat liver and testis membranes. 647 54