Studies on the sugar chains of interferon-gamma from human peripheral-blood lymphocytes

Sugar chains of interferon-gamma (IFN-gamma) from human peripheral-blood lymphocytes (PBL) were liberated by hydrazinolysis. After N-acetylation, the reducing end residues of the sugar chains were tagged with 2-aminopyridine and the pyridylamino (PA-) derivatives were purified by gel filtration and reversed-phase HPLC. Five major PA-sugar chains were obtained. The structure of each PA-sugar chain was estimated by comparing its elution times on anion exchange, reversed-phase, and size-fractionation HPLC with those of PA-sugar chains of IFN-gamma from the human myelomonocyte cell line HBL-38 (Yamamoto, S. et al. (1989) J. Biochem. 105, 547-555) as standards, and also by comparison of their elution times after partial desialylation. The results showed that IFN-gamma (PBL) contained mono- and disialo-biantennary structures with 0 or 1 mol of fucose residue, as found for IFN-gamma (HBL-38), but the N-acetylneuraminyl alpha 2-6 linkage was dominant in IFN-gamma (PBL), unlike IFN-gamma (HBL-38), which contains both N-acetylneuraminyl alpha 2-3 and alpha 2-6 linkages.     

Mast cell degranulating (MCD) peptide and its optical isomer activate GTP binding protein in rat mast cells

The MCD peptide in bee venom induces degranulation in mast cells. The internal calcium concentration of mast cells increased and remained high following MCD stimulation. This calcium increase was blocked by pertussis toxin (Ptx) treatment, suggesting that MCD peptide activates Ptx-sensitive G-protein. Even in the absence of external calcium in the incubation medium, the calcium concentration increased by MCD treatment, but soon returned to the original level. D-MCD, the optical isomer of the MCD peptide, also increased the internal calcium concentration through a Ptx-sensitive pathway. We suggest that cationic clusters at one side of the surface are more important in activating the G-protein than the alpha-helix conformation.