Human serum beta lipoprotein and beta apoprotein

WE have recently prepared the protein moiety or apoprotein of beta lipoprotein (βLP) in a soluble form that is similar but not identical to the parent βLP with respect to immunochemical and optical properties^1-3. The occurrence of lipid-free β-apoprotein in the plasma of normals and patients with abetalipoproteinaemia (ABL) has been inferred from experiments in which antisera to ABL plasma and to the plasma fraction of density greater than 1.21 (d 1.21 infranatant) were found to react with the acetyl and azo-derivatives of βLP⁴. These derivatives differed in immunochemical properties from βLP and seemed to be identical to an antigen present in the plasma of normals or patients with ABL. It was concluded that this antigen was most likely β-apoprotein and that β-apoprotein may exist in an altered antigenic and conformational state in the d 1.21 infranatant fraction. Our study attempts to make a direct comparison of the immunochemical reactivities of β-apoprotein and the chemical derivatives.