Hydrophobic Interactions of Transcobalamin II (TC II) from Mammalian Sera

Abstract

Abstract

The hydrophobic properties of mammalian transcobalamin lis (TC II) were studied by chromatography of radioactive cyanocobalamin (CN[⁵⁷Co]Cbl)-labeled serum on phenyl-Sepharose CL-4B. Mammalian holo TC IIs (CN[⁵⁷Co]Cbl-TC II) exhibited species variability in their affinity for the hydrophobic matrix in the order dog > mouse > human > rat > rabbit. Phenyl-Sepharose chromatography of the isolated CN[⁵⁷Co]Cbl-TC II peaks from gel filtration of dog and rat serum showed no hydrophobic change in dog TC II, but an increase in hydro-phobicity of rat TC II. Phenyl-Sepharose chromatography of CN[⁵⁷Co]Cbl-labeled rabbit serum (holo TC II) and the unlabeled serum (apo TC II) showed apo TC II to be more hydrophobic than holo TC II as has been shown for human TC II (Begley et al., Biochem Biophys Res Commun 103:434-441, 1981). Thus mammalian holo TC lis differ in their hydrophobic properties and apo TC II, in man and rabbit, is more hydrophobic than holo TC II. In addition, isolation of the TC II in some animal sera by gel filtration may result in a TC II that is more hydrophobic than the native molecule.