title: Lipid-protein interactions in high density lipoproteins.
abstract: Delipidated high density lipoprotein (apo-HDL), isolated apolipoproteins apoA-I and apoA-II, S-carboxymethylated apoA-II, apoC-III, the NH(2)- and COOH-terminal CNBr peptides of apoA-II, and the COOH-terminal CNBr peptide of apoA-I were recombined in vitro with [N-C(3)H(3)-choline]phosphatidylcholine (PC) and [N-(14)CH(3)-choline]sphingomyelin (SPM). The lipid-protein complexes were analyzed by ultracentrifugal flotation, agarose gel chromatography and circular dichroism. ApoHDL, apoA-II, and S-carboxymethylated apoA-II readily recombined with PC or SPM to form particles that were similar in size to native HDL. The COOH- but not the NH(2)-terminal CNBr peptide of apoA-II recombined with lipid. ApoA-I and the COOH-terminal CNBr peptide of apoA-I, however, recombined with PC or SPM to only a limited extent, suggesting that protein-protein interactions between apoA-I and apoA-II are important in the integration of apoA-I into recombined lipoprotein particles. Analysis of the recombined lipid-protein complexes by circular dichroism indicated that there was an increase in helical structure concomitant with lipid-protein binding. The reconstituted particles had many of the physical and chemical properties of the native lipoprotein.
mesh_terms: D002845:Chromatography; D002942:Circular Dichroism; D003488:Cyanogen Bromide; D006801:Humans; D008075:Lipoproteins, HDL / Q000097:blood / Q000378:metabolism*; D008297:Male; D010446:Peptide Fragments / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism*; D011485:Protein Binding; D013109:Sphingomyelins / Q000378:metabolism*; D014461:Ultracentrifugation
chemical_list: D008075:Lipoproteins, HDL; D010446:Peptide Fragments; D010713:Phosphatidylcholines; D013109:Sphingomyelins; D003488:Cyanogen Bromide