The structure and properties of human beta-lipoprotein and beta-apoprotein

Little is known about the structure of the protein of serum beta-lipoprotein owing to the insolubility of the delipidated product (beta-apoprotein). Attempts have been made to solubilize the apoprotein (Granda and Scanu, 1966) or a chemical derivative of the apoprotein (Gotto et al., 1968a, b, c; Scanu et al., 1967; Shore and Shore, 1967). This communication describes the preparation of beta-apoprotein by solubilization with sodium decyl sulfate. The apoprotein closely resembles the parent lipoprotein in immunological properties and structural conformation. The circular dichroism and infrared spectrum of beta-lipoprotein indicate a significant amount of pleated sheet, anti-parallel chain (APC) β-structure. This is also true for the apoprotein, except that the molar ellipticity at 216 mμ ([θ′]₂₁₆) is reduced by about 25%. The apoprotein has a fibrillar appearance when viewed with the electron microscope by the technique of negative staining.