Factor J, a human inhibitor of complement C1, is a cationic, highly glycosylated protein.
Factor J (FJ) is a new inhibitor of the complement system. This work supports the fact that FJ is a cationic molecule (pI > or = 9.6 in native conditions, or pI = 8.1 in denaturing conditions) with a high sugar content (40%) that is able to interact with different lectins, suggesting a complex glycosylation. SDS impaired FJ migration in polyacrylamide gel electrophoresis. In Triton-acid-urea-polyacrylamide gel electrophoresis FJ migrated as a complex, dispersed molecule. In contrast, FJ after Smith degradation (dFJ) gave a single, smeared band of M(r) = 23.4 kDa in reducing SDS-PAGE. dFJ retained only 60% of the initial inhibitory activity of intact FJ. When digestions with different proteinases were performed, no modification of activity was observed. After beta-glucuronidase digestion, FJ lost 80% of its initial activity. Consequently, glycosylation plays an important role in the inhibitory activity of FJ.
Jiménez-Clavero
M A
MA
Unidad de Immunología, Hospital La Paz, Madrid, Spain.
González-Rubio
C
C
Fontán
G
G
López-Trascasa
M
M
D002240:Carbohydrate Sequence; D002851:Chromatography, High Pressure Liquid; D003174:Complement C1 Inactivator Proteins / Q000737:chemistry* / Q000302:isolation & purification; D015941:Complement Hemolytic Activity Assay; D004591:Electrophoresis, Polyacrylamide Gel; D006023:Glycoproteins / Q000737:chemistry* / Q000302:isolation & purification; D006801:Humans; D007526:Isoelectric Point; D008969:Molecular Sequence Data
D003174:Complement C1 Inactivator Proteins; D006023:Glycoproteins