Identification and localization of the apoprotein fraction of the bile lipoprotein complex in human gallstones.

The anionic polypeptidic fraction is the protein constituent of the bile lipoprotein complex. Double immunodiffusion and sodium dodecyl sulfate polyacrylamide gel electrophoresis studies show that the anionic polypeptidic fraction is present in human gallstones. In terms of weight percentage, this protein accounts for 0.1% +/- 0.087 (n = 6) of the total weight of gallstones. Immunolocalization studies confirm the presence of the anionic polypeptidic fraction in human gallstones and suggest that this protein is preferentially associated with pigmented layers in gallstones. A speculative role for the anionic polypeptidic fraction in cholesterol nucleation is discussed.