title: Apolipoprotein B is a calcium binding protein.
abstract: Human hepatocarcinoma Hep G2 cells were grown in culture medium containing [45Ca2+]. The secreted lipoproteins of d less than 1.063 g/ml and d 1.063-1.21 g/ml were isolated from the culture media and analyzed by 3.3% and 7% SDS-polyacrylamide gel electrophoresis. Radioactivity profiles of [45Ca] from the gels showed that the peak of radioactivity corresponded to the apolipoprotein B band. The molar ratio of the incorporated [45Ca2+] and apolipoprotein B was close to unity. No radioactivity was found associated with any other secreted apolipoproteins. To confirm these findings, apolipoprotein B-containing lipoproteins were precipitated with anti-apolipoprotein B and high density lipoproteins were precipitated with anti-apolipoprotein A-I. Only the former precipitate was radioactive. These results suggest that apolipoprotein B is a calcium binding protein.
mesh_terms: D000818:Animals; D016632:Apolipoprotein A-I; D001054:Apolipoproteins A / Q000378:metabolism; D001055:Apolipoproteins B / Q000096:biosynthesis / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002460:Cell Line; D006801:Humans; D008114:Liver Neoplasms, Experimental
chemical_list: D016632:Apolipoprotein A-I; D001054:Apolipoproteins A; D001055:Apolipoproteins B; D002135:Calcium-Binding Proteins; D002118:Calcium