Soluble complex formation between low-density lipoprotein and glycosaminoglycans. A 2H and 31P-NMR, and quasi-elastic light scattering study.
Soluble complex formation between LDL and heparin (HEP) and chondroitin sulfate (CS) has been studied by 2H- and 31P-NMR and light scattering. The 2H-NMR linewidths of [2H]HEP and [2H]C4S increase substantially upon binding to LDL, with the [2H]HEP linewidths broader at low glycosaminoglycan (GAG)/low density lipoprotein (LDL) ratios. Preliminary analysis of the bound C2H3 group correlation times suggests that the observed linewidths are determined by the complex size, and that both [2H]GAGs have similar motions when bound to LDL. The 31P-NMR data demonstrate that large LDL-HEP complexes (diameter approx. 50 nm) are formed only over a narrow range of HEP concentrations, whereas the size of LDL-CS complexes increases continuously over the range of CS concentrations studied, reaching values of 32-35 nm for both C4S and C6S. At the lower protein concentrations studied by light scattering (less than or equal to 1 mg/ml), the same trends are observed, although the mean diameters are less than those estimated by 31P-NMR. Soluble complex formation was unaffected by the presence of 2 mM Ca2+. Dilution studies demonstrate that complex size varies with protein concentration. The binding of GAGs to LDL was also examined by HEP-CS competition studies. HEP has the higher affinity while no differences in binding could be detected between C4S and C6S.
Fenske
D B
DB
Department of Chemistry, Simon Fraser University, Burnaby, B.C., Canada.
Cushley
R J
RJ
D002118:Calcium / Q000494:pharmacology; D002809:Chondroitin Sulfates / Q000378:metabolism; D006025:Glycosaminoglycans / Q000378:metabolism*; D006493:Heparin / Q000378:metabolism; D008027:Light; D008077:Lipoproteins, LDL / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008970:Molecular Weight; D011973:Receptors, LDL / Q000378:metabolism; D012542:Scattering, Radiation
D006025:Glycosaminoglycans; D008077:Lipoproteins, LDL; D011973:Receptors, LDL; D006493:Heparin; D002809:Chondroitin Sulfates; D002118:Calcium