Phospholipid-protein interactions in human low density lipoprotein detected by phosphorus-31 nuclear magnetic resonance

Abstract

31P NMR spectra of human low density lipoprotein (LDL) were obtained and the major phospholipid components identified. Analysis of the spectra revealed 2 phospholipid environments: 1 occupied by 4/5 of the phospholipid with high resolution resonances possessing properties similar to phospholipids in vesicles, and a 2nd occupied by 1/5 of the phospholipid with broad lines indicative of immobilization. Limited trypsin treatment of the particle cleaved all of the B peptide into smaller MW peptides which remained with the particle. Trypsin-treated LDL eluted from a Sepharose CL-6B column similarly to native LDL so that the modified particle remained intact. 31P NMR spectra of trypsin-treated LDL showed little or no immobilized phospholipid. The immobilization in the native LDL particle is attributed to lipid-protein interactions between 1/5 of the phospholipid and the B peptide.