Separation of the apoprotein components of human serum high density lipoprotein: chromatofocusing, a new simple technique

Abstract

The high-density lipoproteins (HDL) are a heterogeneous group of particles operationally defined as those lipoproteins isolated between the densities of 1.063 and 1.210 g/ml. About 50% of HDL mass is protein, 30% is phospholipid, and 20% is cholesterol [l]. Of the several apolipoproteins present, apo A-I and apo A-II are major components; minor polypeptides include apo C-I, apo C-II, apo C-III, apo D and apo E [2-41. Apoprotein A-I and apoprotein A-II constitute about 90% of total HDL protein, with a ratio of apo A-I to APO-II of 3 : 1 in both HDL, and HDL, [5]. Apoprotein C is present in the HDL density range of humans in small amounts, and comprises 5-10% of HDL, protein, and l-2% of HDL, protein [6]. The most used methods to separate different apoproteins from HDL are gel filtration combined with DEAE cellulose ion-exchange chromatography [7,8]. In this study, chromatofocusing of human serum apoHDL with and without urea has been employed to fractionate different apoproteins, and slab gel electrophoresis has been performed to study the purity of fractions.