Studies on the pre-alpha-lipoprotein of human serum. II. Evidence for the presence of an albumin-apo-A-I complex.

By combined column affinity chromatography and preparative electrophoresis, a lipoprotein was isolated from the electrophoretically defined pre-alpha-region. The isolated fraction, designated Fraction II1, demonstrated one band after electrophoresis in agarose, in polyacrylamide, and in sodium dodecylsulphate containing polyacrylamid. Double diffusion experiments disclosed the presence of albumin and apolipoprotein-A-I within the fraction. After reduction with mercaptoethanol and subsequent electrophoresis in sodium dodecylsulphate containing polyacrylamide gel, two bands appeared. One of the bands had an electrophoretic mobility similar to albumin monomer (mol.wt 67,000), the other had the same electrophoretic mobility as apolipoprotein-A-I with a mol.wt of 28,400. It is suggested that Fraction II1 contains an albumin-apolipoprotein-A-I complex.