Immunoenzyme Assessment of Human ApoB-Lipoprotein Binding to Immobilized Receptor of Low Density Lipoproteins. 2. Binding of Isolated Lipoproteins

V. P. Tsibulsky,¹ V. V. Yakushkin,^1,2 and S. N. Preobrazhensky³

¹Institute of Experimental Cardiology, Russian Cardiology Complex, ul. 3-ya Cherepkovskaya 15a, Moscow, 121552 Russia; fax: (7-095) 414-66-99.

²To whom correspondence should be addressed.

³USANA Research Company, Salt Lake City, Utah, USA.

Submitted February 19, 1997.

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The receptor of low density lipoproteins (LDL-receptor) from bovine adrenal cortex membranes was immobilized in standard 96-well polystyrene plates using monoclonal V5-antibodies to the LDL-receptor. The binding of the immobilized LDL-receptor with human low density lipoproteins (LDL) and very low density lipoproteins (VLDL) was determined using peroxidase-labelled antibodies to human apoB. The value of K_d for the interaction of LDL with the immobilized LDL-receptor for 40 samples of LDL was found to be from 5 to 20 µg apoB per ml. The immobilized LDL-receptor failed to bind LDL modified by acetylation or malonic dialdehyde, while the binding of non-modified LDL to the immobilized LDL-receptor was inhibited in the presence of EDTA, which is known to be specific for the interaction of LDL with the LDL-receptor. Unlike LDL, VLDL were more variable in the binding to the LDL-receptor. The value of K_d for the interaction of VLDL with the LDL-receptor for 40 samples of VLDL was found to be from 0.5 to 10 µg apoB per ml. Thus, the described method is suggested to study the interaction of apoB-containing lipoproteins with the LDL-receptor.

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KEY WORDS: low density lipoprotein receptor, low density lipoproteins, very low density lipoproteins, ligand--receptor interaction, immunoenzyme method.

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