Anionic polypeptide fraction (APF) and calcium-binding preparations of APF/CBP could reflect different sources protein (CBP) are two very similar, small, amphipathic, and separation procedures, leading to partly degraded highly anionic proteins that are present in high concentraand/or denatured protein and varied association of bile tions in both normal and pathological bile and all types of salts, lipids, bile pigments, and detergents. The present gallstones.1-3 APF, the phospholipid-binding apoprotein of the study presents new methods for isolation and purifica-bile pigment-lipoprotein complex of bile, 4,5 is involved in the tion of APF/CBP, and characterizes the preparations secretion of cholesterol and phospholipids into bile.6 CBP thus obtained. It was found that isolation by selective binds calcium tightly and promotes the precipitation of calprecipitation of proteins from fresh T-tube bile by added cium salts when bound to mucin, 7 but inhibits calcium salt calcium chloride, followed by demineralization with eth-precipitation when not bound to mucin.7-9 APF, however, is ylenediaminetetraacetic acid (EDTA), removal of salts, also found in gallstones, 10,11 where it is uniquely localized to lipids, and some pigment by Sephadex LH-20, and serial the pigmented zones, interposed between the mucin matrix ultrafiltration yields the purest preparations. Though and the calcium-pigment deposits.11 These properties suggest free of lipids, bile salts, detergents, and most pigments, that APF and/or CBP may play key roles in the regulation these new preparations all show the same 7-kd and 12-of the precipitation of calcium salts from supersaturated bile, kd bands on sodium dodecyl sulfate-polyacrylamide gel and the deposition of these salts on the structural mucin electrophoresis (SDS-PAGE), the same major peaks on matrix of the gallstones.
1,2,11hydrophobic high-performance liquid chromatographyNeither APF nor CBP has been fully purified or sequenced, (HPLC), and retain the self-associative, lipid-and cal-and the various preparations from different laboratories, 4,5,7-cium-binding functions, typical of older preparations ob-13 isolated from different sources using different procedures, tained by potentially denaturative procedures. The var-often exhibit disparate properties, even though all display ied properties among APF/CBP preparations are thus 12-kd as well as 7-kd bands on sodium dodecyl sulfate-polyapparently related mainly to their content of different acrylamide gel electrophoresis (SDS-PAGE), and all exhibit proportions of two major components, lipid-binding APF immunologic cross-reactivities and very similar amino acid and calcium-binding CBP. Immunologic cross-reactions compositions. 13 The present collaborative communication indicate common epitopes, and amino acid analyses are from these laboratories presents new isolation methods and also similar, suggesting that APF and CBP may have compares the properties of these preparations with those of the same polypeptide backbone, but differ because of older pr...
