Role of transcobalamins I, II, and III in the transfer of vitamin B12 to human bone marrow cells in vitro.
A study of the uptake of transcobalamin-bound 57Co-cyanocobalamin by suspensions of human bone marrow cells has indicated that these cells can take up vitamin B12 from all 3 transcobalamins (I, II, and III).  Similar transport processes were involved in the uptake from the 3 transcobalamins; uptake was dependent on the presence of calcium ions, cellular respiration and free sulphydryl groups.  These results suggest that contrary to current belief, all 3 transcobalamins play a role in the transfer of vitamin B12 to tissue cells.
D001692:Biological Transport / Q000187:drug effects; D001798:Blood Proteins / Q000378:metabolism*; D001853:Bone Marrow / Q000187:drug effects / Q000378:metabolism*; D001854:Bone Marrow Cells; D003486:Cyanides / Q000494:pharmacology; D003864:Depression, Chemical; D004492:Edetic Acid / Q000494:pharmacology; D006801:Humans; D007460:Iodoacetamide / Q000494:pharmacology; D014155:Transcobalamins / Q000378:metabolism*; D014805:Vitamin B 12 / Q000378:metabolism*
D001798:Blood Proteins; D003486:Cyanides; D014155:Transcobalamins; D004492:Edetic Acid; D014805:Vitamin B 12; D007460:Iodoacetamide