Protein composition of Lp(a) lipoprotein from human plasma

Abstract

The apolipoprotein composition of purified human Lp(a) lipoprotein was investigated by SDS—polyacrylamide gel electrophoresis and immunochemically. The lipoprotein contains two different polypeptides. One is identical by its app. M _r of ∼250000 and immunologically with apolipoprotein B of LDL (B‐100). The other polypeptide has a higher app. M _r (∼350000) and stains strongly with the periodate‐Schiff's reagent. This high‐M _r glycoprotein contains the specific Lp(a) immunoreactivity but does not react with antibodies against apo B. Apo B and Lp(a)‐protein seem to be linked by disulfide bonds in the native lipoprotein. The unreduced detergent delipidized protein moiety from Lp(a) lipoprotein shows a single band of M _r ∼700000 in SDS—polyacrylamide gel electrophoresis and the immunoprecipitates formed against anti‐Lp(a) and anti‐apo B by the unreduced protein show a reaction of immunological identity.