Transgenic plants expressing cobalamin binding proteins

Abstract

The present invention relates to the use of transgenic plants for the expression of vitamin B12 (cobalamin) binding proteins. Plant cells are transformed with nucleotide sequences adapted for expression and secretion of vitamin B12 binding proteins. The present invention also relates to the use of recombinant vitamin B12 binding proteins from plants in analytical tests and treatment of vitamin B12 deficiency. Also disclosed is a method for purification of recombinant vitamin B12 binding proteins.

What is claimed is: 
     
         1 . A method of internalizing B12 within a cell via cubilin, the method comprising:
 a) combining intrinsic factor that has plant specific glycosylation with B12 to form an intrinsic factor-B12 complex, and   b) contacting cubilin located on a cell surface with the complex such that the complex binds to cubilin and B12 is internalized within the cell.   
     
     
         2 . A method of delivering B12 to a subject, the method comprising administering, to the subject, an intrinsic factor-B12 complex where the intrinsic factor has plant specific glycosylation and the complex binds to cubilin in the subject. 
     
     
         3 . The method of  claim 2 , wherein the subject has a cobalamin deficiency. 
     
     
         4 . The method of  claim 3 , wherein the cobalamin deficiency is caused by either low levels or no detectable levels of at least one of the group consisting of intrinsic factor and haptocorrin.