The self-association of the apo-Gln-I and apo-Gln-II polypeptides of human high density serum lipoproteins.

The major polypeptide components of human high density lipoprotein, apo-Gln-I and apo-Gln-II, self-associate at pH 8.3 and ionic strength 0.045. The dimeric (MW = 56,800) association constant for apo-Gln-I is 1.3 X 10(4)liters/mol. apo-Gln-II is tetrameric at all experimentally accessible concentrations. Self-association of apo-Gln-I is accompanied by minor conformational alterations distinct from that induced by saturating levels of bound amphiphilic ligands. These results are discussed with respect to the design of reconstitution experiments between the apoproteins and lipids.