Characterization of deglycosylated human urinary colony-stimulating factor (CSF-1)

Abstract

1. 1. Isolation of CSF-1 from human urine was performed through five purification steps. These include concentration by dialysis, silica gel absorption, hydrophobic chromatography and phenyl-Sepharose CL-6B, Fast Protein Liquid Chromatography (FPLC) and finally preparative electrophoresis on polyacrylamide gels. These methods have been reported in a previous paper (Tao et al., 1987). 2. 2. The isolated CSF-1 which exhibits a one band pattern on SDS-PAGE under non-reducing conditions after Coosmassie Blue and silver stainings, CSF-1 was purified 100,000-fold and has a specific activity of 2.16 x 10 7 units/mg protein. Its apparent M r is 57,000 with an isoelectric point pI = 5.8–6.0 CSF-l is a glycoprotein with 40% of carbohydrate (w/w). 3. 3. An almost complete removal of the carbohydrate moiety from CSF-1 was obtained after treatment with trifluoromethanesulfonic (TFMS) acid followed by gel filtration on Sephadex G-25 (Fine). The deglycosylated (DG) CSF-1 possesses an apparent M r of 38,000 and an isoelectric point, pI: 6.2 as compared to native-CSF-1 (N-CSF-1), M r = 57,000 and pI = 5.8 respectively. 4. 4. The TFMS treatment did not alter the activities of CSF-1 as shown by biological assay and receptor binding assay. The thermostability experiment revealed that DG-CSF-1 was less stable than N-CSF-1. The circular dichroism spectra (CD) of N-CSF-1 and DG-CSF-1 were different. 5. 5. The features of interaction of iodinated-N-CSF-1 and iodinated-DG-CSF-1 with single cell suspensions from human peritoneal macrophage were studied. The binding activity of peritoneal macrophage was the highest among all cells examined. The carbohydrates compositions of DG-CSF, the N-acetylglucosamine and galactosamine are established.