Molecular basis for the microheterogeneity of human complement factor B.
The involvement of sialic acids in the microheterogeneity of human complement factor B was investigated. Desialylation kinetics revealed all the charge intermediates from a complex native to a homogeneous form. The relation between this heterogeneity and posttranslational events was explored in cultured hepatoma cells. Intracellular factor B exhibited the same isoelectric focusing pattern as the desialylated purified protein, whereas a highly heterogeneous form was secreted. In contrast, when N-glycosylation was prevented by tunicamycin, both intracellular and secreted forms focused like intracellular factor B from control cultures. These data lead to the conclusion that the microheterogeneity of human factor B results from different degrees of sialylation of its N-glycans.
Garnier
G
G
Institut National de la Santé et de la Recherche Médicale, Unité 78, Bois-Guillaume, France.
Davrinche
C
C
Charlionet
R
R
Fontaine
M
M
D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D011415:Complement Factor B / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004792:Enzyme Precursors / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D007163:Immunosorbent Techniques; D007525:Isoelectric Focusing; D007700:Kinetics; D008113:Liver Neoplasms / Q000378:metabolism*; D008970:Molecular Weight; D019158:N-Acetylneuraminic Acid; D009439:Neuraminidase / Q000378:metabolism; D012794:Sialic Acids / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014415:Tunicamycin / Q000494:pharmacology
D004792:Enzyme Precursors; D012794:Sialic Acids; D014415:Tunicamycin; D009439:Neuraminidase; D011415:Complement Factor B; D019158:N-Acetylneuraminic Acid