Corrinoid specificity of cytosolic cobalamin-binding protein of Euglena gracilis z.
To elucidate the corrinoid specificity of the cytosolic cobalamin-binding protein of Euglena gracilis, inhibition of the binding of radioactive cyanocobalamin to the cytosolic binding protein was studied with a variety of cobalamin analogues. The cytosolic cobalamin-binding protein showed an absolute requirement for the alpha-axial ligand (the cobalt-coordinated nucleotide) in cobalamin binding, but was not able to recognize certain differences in the base or ribose moiety. Regarding the contributions of the b-, d-, and e-propionamide side chains in the binding of cobalamin to the cytosolic protein, the order of the contributions was shown to be b > d > e; in particular the b-propionamide side chain was essential for the formation of the protein-cobalamin complex. No involvement of the beta-axial ligand or the alkanolamine group in the binding of cobalamin to the protein was found.
Watanabe
F
F
Laboratory of Nutrition and Food Science, Hagoromo-gakuen College, Osaka.
Nakano
Y
Y
Tamura
Y
Y
Stupperich
E
E
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D045728:Corrinoids; D003600:Cytosol / Q000737:chemistry; D005056:Euglena gracilis / Q000737:chemistry*; D013329:Structure-Activity Relationship; D014155:Transcobalamins / Q000378:metabolism*; D014805:Vitamin B 12 / Q000031:analogs & derivatives / Q000737:chemistry* / Q000378:metabolism*
D045728:Corrinoids; D014155:Transcobalamins; D014805:Vitamin B 12