1. The Heterogeneity of the High Molecular Weight B12 Binder in Serum
- Author
-
Christine Lawrence
- Subjects
Electrophoresis ,Male ,Paper ,Immunology ,Size-exclusion chromatography ,Beta-Globulins ,Biochemistry ,Blood serum ,Column chromatography ,Transcobalamin ,Alpha-Globulins ,Humans ,Cyanocobalamin ,Cellulose ,Chromatography ,Binding Sites ,Chemistry ,Blood Proteins ,Cell Biology ,Hematology ,Blood Protein Electrophoresis ,Blood proteins ,Molecular Weight ,Cobalt Isotopes ,Vitamin B 12 ,Blood chemistry ,Sephadex ,Chromatography, Gel ,Female - Abstract
The binding of vitamin B12 by serum proteins was studied by separating Co57B12-enriched serum by Sephadex gel filtration, column chromatography with DEAE-cellulose, and paper electrophoresis. Each method of separation yielded two discrete B12-binding fractions. However, the analysis of each serum by all three separation technics indicated that one of the fractions was, in each case, bipartite. The "high" molecular weight B12-binding fraction defined by Sephadex gel filtration consisted of transcobalamin I and just part of the transcobalamin II fraction. The remaining portion of transcobalamin II was eluted from Sephadex gel in a "low" molecular weight fraction. Thus, transcobalamin II, equivalent to the β-globulin B12-binder, consisted of both "high" and "low" molecular weight components. This suggests that there are at least three serum proteins that can bind vitamin B12: two β-globulins, together comprising the transcobalamin II fraction and differing in molecular weight; and transcobalamin I.
- Published
- 1969