ISOLATION AND CHARACTERIZATION OF GRANCALCIN, A NOVEL 28 KDA EF-HAND CALCIUM-BINDING PROTEIN FROM HUMAN NEUTROPHILS

A novel 28 kDa protein, which we have named 'grancalcin', has been identified in human neutrophils. The protein was isolated from the cytosol and found to be a homodimer, with an apparent molecular mass of 55 kDa on gel filtration. Polyclonal antibodies were raised to the native protein, N-Terminal sequence analysis and tryptic-peptide sequence analysis was performed. The protein exhibits sequence similarity to sorcin, a 24 kDa calcium-binding protein overexpressed in certain multi-drug-resistant cell lines. It appears to be a member of the EF-hand family of calcium-binding proteins. The association of a high proportion of this protein with the membranes and granules in the presence of physiological concentrations of calcium may indicate a role in granule-membrane fusion and degranulation.