Improved method for the purification of biologically active transcobalamin II.

Transcobalamin II (TC II) was purified about 300,000-fold from Cohn fraction III using a modification of the procedure described by Allen and Majerus (J. Biol. Chem. 247, 7709-7717 (1972)). The simplified method incorporated isoelectric precipitation of the TC II into the purification scheme which permitted the elimination of two column chromatographic steps originally reported by the above workers. The final preparation had 26.7 mug of vitamin B12 (B12) bound per mg of protein and an A280/A361 ratio of 2.05, both of which are in good agreement with the reported values. The purified TC II was biologically active with respect to its ability to facilitate penetration of B12 into HeLa cells in tissue culture.