Chick serum contains two cholecalciferol-binding proteins, one of which binds mainly cholecalciferol (cholecalciferol-binding protein) and the other binds 25-hydroxycholecalciferol (25-hydroxycholecalciferol-binding protein). By means of Cohn fractionation, (NH4)2SO4 precipitation, gel filtration on Sephadex G-200, ion-exchange chromatography on DEAE-Sephadex and an additional gel-filtration step on Sephadex G-100, these two binding proteins were purified. Both proteins possess β-globulin mobility on analytical polyacrylamide-disc-gel electrophoresis, a sedimentation coefficient of 3.5S and approximate molecular weights of 60000 for the cholecalciferol-binding protein and 54000 for the 25-hydroxycholecalciferol-binding protein. Sera obtained from rat, pig, human and monkey were shown to contain a single binding protein that is responsible for the transport of both cholecalciferol and 25-hydroxycholecalciferol. In the toad the lipoproteins are used for the transport of these two steroids.
The transporting proteins of cholecalciferol and 25-hydroxycholecalciferol in serum of chicks and other species. Partial purification and characterization of the chick proteins
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S. Edelstein, D. E. M. Lawson, E. Kodicek; The transporting proteins of cholecalciferol and 25-hydroxycholecalciferol in serum of chicks and other species. Partial purification and characterization of the chick proteins. Biochem J 1 November 1973; 135 (3): 417–426. doi: https://doi.org/10.1042/bj1350417
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