Association of the macrophage activating factor (MAF) precursor activity with polymorphism in vitamin D-binding protein.
BACKGROUND
Serum vitamin D-binding protein (Gc protein or DBP) is a highly expressed polymorphic protein, which is a precursor of the inflammation-primed macrophage activating factor, GcMAF, by a cascade of carbohydrate processing reactions. In order to elucidate the relationship between Gc polymorphism and GcMAF precursor activity, we estimated the phagocytic ability of three homotypes of Gc protein, Gc1F-1F, Gc1S-1S and Gc2-2, through processing of their carbohydrate moiety.


METHODS
We performed Gc typing of human serum samples by isoelectric focusing (IEF). Gc protein from human serum was purified by affinity chromatography with 25-hydroxyvitamin D3-sepharose. A phagocytosis assay of Gc proteins, modified using beta-glycosidase and sialidase, was carried out.


RESULTS
The Gc1F-1F phenotype was revealed to possess Galbeta1-4GalNAc linkage by the analysis of GcMAF precursor activity using beta1-4 linkage-specific galactosidase from jack bean. The GcMAF precursor activity of the Gc1F-1F phenotype was highest among three Gc homotypes.


CONCLUSIONS
The Gc polymorphism and carbohydrate diversity of Gc protein are significant for its pleiotropic effects.
Nagasawa
Hideko
H
Department of Biological Science and Technology, Faculty of Engineering, The University of Tokushima, Tokushima 770-8503, Japan.
Sasaki
Hideyuki
H
Uto
Yoshihiro
Y
Kubo
Shinichi
S
Hori
Hitoshi
H
D000328:Adult; D000818:Animals; D050260:Carbohydrate Metabolism; D002241:Carbohydrates / Q000737:chemistry; D002846:Chromatography, Affinity; D005260:Female; D006801:Humans; D007525:Isoelectric Focusing; D008222:Lymphokines / Q000378:metabolism*; D051379:Mice; D008875:Middle Aged; D008958:Models, Molecular; D010587:Phagocytosis; D010641:Phenotype; D011110:Polymorphism, Genetic; D011487:Protein Conformation; D011498:Protein Precursors / Q000378:metabolism*; D014809:Vitamin D-Binding Protein / Q000097:blood* / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D001616:beta-Galactosidase / Q000378:metabolism
D002241:Carbohydrates; D008222:Lymphokines; D011498:Protein Precursors; D014809:Vitamin D-Binding Protein; C035408:macrophage aggregation factor; D001616:beta-Galactosidase