Physical-chemical interaction of heparin and human plasma low-density lipoproteins
- 25 August 1987
- journal article
- research article
- Published by American Chemical Society (ACS) in Biochemistry
- Vol. 26 (17), 5513-5518
- https://doi.org/10.1021/bi00391a045
Abstract
This study characterizes the physical-chemical interactions of heparin with human plasma low-density lipoproteins (LDL). A high reactive heparin (HRH) specific for the surface determinants of LDL was isolated by chromatography of commerical bovine lung heparin on LDL immobilized to AffiGel-10. HRH was derivatized with fluoresceinamine and repurified by affinity chromatography, and its interaction with LDL in solution was monitored by steady-state fluorescence polarization. Binding of LDL to fluorescenamine-labeled HRH (FL-HRH) was saturable, reversible, and specific; HRH stoichiometrically displaced FL.cntdot.HRH from the soluble complex, and acetylation of lysine residues on LDL blocked heparin binding. Titration FL.cntdot.HRH with excess LDL yielded soluble complexes with two LDL molecules per heparin chain (Mr 13,000) characterized by an apparent Kd of 1 .mu.M. Titration of LDL with excess HRH resulted in two classes of heparin binding with two and five heparin molecules bound per LDL and apparent Kd values of 1 and 10 .MU., respectively. At physiological pH and ionic strength, the soluble HRH-LDL complexes were maximally precipitated with 20-50 mM Ca2+. Insoluble complexes contained 2-10 HRH molecules per LDL with the final product stiochiometry dependent on the ratio of the reactants. The affinity of HRH for LDL in the insoluble complexes was estimated between 1 and 10 .mu.M. Insoluble LDL-heparin complexes were readily dissociated with 1.0 M NaCl, and their formation was prevented by acetylation of the lysine residues on LDL.This publication has 29 references indexed in Scilit:
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