Inhibition of the binding of low-density lipoprotein to its cell surface receptor in human fibroblasts by positively charged proteins. 1978

M S Brown, and T F Deuel, and S K Basu, and J L Goldstein

A group of proteins and polyamino acids with positively charged domains were shown to inhibit the binding of 125I-LDL to its receptor on the surface of human fibroblasts. The list of inhibitory proteins included platelet factor 4 (which has a cluster of lysine residues at its carboxyl terminus), two lysine-rich histones, poly-L-lysines of chain length greater than 4, and protamine. These proteins were effective in the concentration range of 5--10 microgram/ml. Two other positively charged proteins, lysozyme and avidin, did not inhibit 125I-LDL binding. Kinetic studies suggested that protamine was not acting simply as a competitive inhibitor with regard to the LDL receptor. In light of previous data showing that polyanions such as heparin and polyphosphates also inhibit 125-I-LDL binding to its cell surface receptor, the current findings suggest that charge interactions are important in this binding reaction. In a related series of studies, a number of glycoproteins and their asialo derivatives as well as a number of sugar phosphates failed to inhibit 125I-LDL binding to its receptor in fibroblasts.

UI MeSH Term Description Entries
D007526 Isoelectric Point The pH in solutions of proteins and related compounds at which the dipolar ions are at a maximum. Isoelectric Points,Point, Isoelectric,Points, Isoelectric
D008077 Lipoproteins, LDL A class of lipoproteins of small size (18-25 nm) and light (1.019-1.063 g/ml) particles with a core composed mainly of CHOLESTEROL ESTERS and smaller amounts of TRIGLYCERIDES. The surface monolayer consists mostly of PHOSPHOLIPIDS, a single copy of APOLIPOPROTEIN B-100, and free cholesterol molecules. The main LDL function is to transport cholesterol and cholesterol esters to extrahepatic tissues. Low-Density Lipoprotein,Low-Density Lipoproteins,beta-Lipoprotein,beta-Lipoproteins,LDL(1),LDL(2),LDL-1,LDL-2,LDL1,LDL2,Low-Density Lipoprotein 1,Low-Density Lipoprotein 2,LDL Lipoproteins,Lipoprotein, Low-Density,Lipoproteins, Low-Density,Low Density Lipoprotein,Low Density Lipoprotein 1,Low Density Lipoprotein 2,Low Density Lipoproteins,beta Lipoprotein,beta Lipoproteins
D010978 Platelet Factor 4 A CXC chemokine that is found in the alpha granules of PLATELETS. The protein has a molecular size of 7800 kDa and can occur as a monomer, a dimer or a tetramer depending upon its concentration in solution. Platelet factor 4 has a high affinity for HEPARIN and is often found complexed with GLYCOPROTEINS such as PROTEIN C. Antiheparin Factor,CXCL4 Chemokine,Chemokine CXCL4,Heparin Neutralizing Protein,PF4 (Platelet Factor 4),gamma-Thromboglobulin,CXCL4, Chemokine,Chemokine, CXCL4,gamma Thromboglobulin
D011107 Polylysine A peptide which is a homopolymer of lysine. Epsilon-Polylysine,Poly-(Alpha-L-Lysine),Epsilon Polylysine
D011479 Protamines A group of simple proteins that yield basic amino acids on hydrolysis and that occur combined with nucleic acid in the sperm of fish. Protamines contain very few kinds of amino acids. Protamine sulfate combines with heparin to form a stable inactive complex; it is used to neutralize the anticoagulant action of heparin in the treatment of heparin overdose. (From Merck Index, 11th ed; Martindale, The Extra Pharmacopoeia, 30th ed, p692) Protamine,Protamine Sulfate,Protamine Chloride,Chloride, Protamine,Sulfate, Protamine
D011485 Protein Binding The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments. Plasma Protein Binding Capacity,Binding, Protein
D011955 Receptors, Drug Proteins that bind specific drugs with high affinity and trigger intracellular changes influencing the behavior of cells. Drug receptors are generally thought to be receptors for some endogenous substance not otherwise specified. Drug Receptors,Drug Receptor,Receptor, Drug
D001779 Blood Coagulation Factors Endogenous substances, usually proteins, that are involved in the blood coagulation process. Clotting Factor,Coagulation Factors,Blood Coagulation Factor,Clotting Factors,Coagulation Factor,Coagulation Factor, Blood,Coagulation Factors, Blood,Factor, Coagulation,Factors, Coagulation,Factor, Blood Coagulation,Factor, Clotting,Factors, Blood Coagulation,Factors, Clotting
D002460 Cell Line Established cell cultures that have the potential to propagate indefinitely. Cell Lines,Line, Cell,Lines, Cell
D002788 Cholesterol Esters Fatty acid esters of cholesterol which constitute about two-thirds of the cholesterol in the plasma. The accumulation of cholesterol esters in the arterial intima is a characteristic feature of atherosclerosis. Cholesterol Ester,Cholesteryl Ester,Cholesteryl Esters,Ester, Cholesterol,Ester, Cholesteryl,Esters, Cholesterol,Esters, Cholesteryl

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