Binding of transition metals by apolipoprotein A-I-containing plasma lipoproteins: inhibition of oxidation of low density lipoproteins.
We have found transition metals tightly bound to apolipoprotein A-I-containing lipoproteins [Lp(A-I)] isolated by selected affinity immunosorption from human serum. Prominent among the metal ions detected were iron and copper. By immunoblotting the proteins of Lp(A-I), we detected both transferrin and ceruloplasmin. The transferrin-containing Lp(A-I) particles, isolated by selected affinity immunosorption against transferrin, were larger (mean diameter of 14.2 nm) and had a higher protein content than most high density lipoproteins (HDL). Ultracentrifugally isolated HDL were found to contain much less transferrin, whereas transferrin was found associated with apolipoprotein A-I from the greater than 1.21-g/ml ultracentrifugal fraction. This suggests that the complex is not recovered in the classic HDL density interval because of its very high density. HDL inhibit copper-catalyzed oxidation of low density lipoproteins (LDL) in vitro. We have found that immunoisolated Lp(A-I) are an order of magnitude more effective in inhibiting the oxidation of LDL than ultracentrifugally isolated HDL, on the basis of protein mass. When the Lp(A-I) particles containing transferrin and ceruloplasmin were removed from the bulk of Lp(A-I), inhibition of the in vitro oxidation of LDL was significantly decreased.
Kunitake
S T
ST
Cardiovascular Research Institute, University of California, San Francisco 94143-0130.
Jarvis
M R
MR
Hamilton
R L
RL
Kane
J P
JP
D016632:Apolipoprotein A-I / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure; D002570:Ceruloplasmin / Q000302:isolation & purification / Q000378:metabolism; D002784:Cholesterol / Q000032:analysis; D002788:Cholesterol Esters / Q000032:analysis; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D015151:Immunoblotting; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000097:blood / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000097:blood / Q000302:isolation & purification / Q000378:metabolism*; D008297:Male; D008670:Metals / Q000378:metabolism*; D010084:Oxidation-Reduction; D011485:Protein Binding; D014168:Transferrin / Q000302:isolation & purification / Q000378:metabolism / Q000648:ultrastructure; D014280:Triglycerides / Q000032:analysis
D016632:Apolipoprotein A-I; D002788:Cholesterol Esters; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D008670:Metals; D014168:Transferrin; D014280:Triglycerides; D002784:Cholesterol; D002570:Ceruloplasmin