Isoelectrofocusing phenotype and relative concentration of transcobalamin II isoproteins related to the codon 259 Arg/Pro polymorphism.
We investigated transcobalamin II (TC) isoelectrofocusing (IEF) phenotype and codon 259 polymorphism, in Caco-2 and HT-29 cells and in blood drawn from 39 healthy Caucasians. Caco-2 cells expressed a single TC variant (259-Arg), while HT-29 cells expressed TC with either Arg or Pro at codon 259 and exhibited two isoproteins in IEF with urea, but only one in IEF without urea. Among the Caucasians, 7 subjects expressed the TC 259-Arg variant, 10 the 259-Pro variant, and 22 were heterozygous. The TC 259-Pro isoprotein issued from HT-29 cells and heterozygous caucasian sera, was, respectively, 2. 4-fold and 1.6-fold higher than the TC 259-Arg isoprotein. Apo-TC and vitamin B12 serum concentrations in 259-Pro homozygotes were, respectively, 1.7 and 1.4-fold higher than those in 259-Arg homozygotes (p<0.005 and p=0.05). In conclusion, the 259-Arg/Pro polymorphism yields two TC variants only titratable in denaturing conditions and affects the blood level of both Apo-TC and vitamin B12.
Namour
F
F
Laboratoire de Pathologie Cellulaire et Moléculaire en Nutrition, EP CNRS 616, Vandoeuvre les Nancy, Cedex, 54505, France.
Guy
M
M
Aimone-Gastin
I
I
de Nonancourt
M
M
Mrabet
N
N
Guéant
J L
JL
D000328:Adult; D000368:Aged; D001059:Apoproteins / Q000097:blood / Q000235:genetics; D001120:Arginine / Q000235:genetics; D018938:Caco-2 Cells; D019073:HT29 Cells; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D007525:Isoelectric Focusing; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000235:genetics; D010641:Phenotype; D011110:Polymorphism, Genetic; D011392:Proline / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics*; D014155:Transcobalamins / Q000235:genetics*; D014805:Vitamin B 12 / Q000097:blood; D044465:White People / Q000235:genetics
D001059:Apoproteins; D009363:Neoplasm Proteins; D020033:Protein Isoforms; D014155:Transcobalamins; D001120:Arginine; D011392:Proline; D014805:Vitamin B 12