Purification and characterization of thiol-specific antioxidant protein from human red blood cell: a new type of antioxidant protein.

A thiol-specific antioxidant protein (Protector Protein, PRP) was purified from human red blood cells (RBC). The PRP exists as a predominant protein in human RBC, which showed distinct thiol-specific antioxidant activities in the presence of dithiothreitol (DTT) as a reducing equivalent. The human RBC PRP (HRPRP) completely inhibited visible absorption spectral changes of oxyhemoglobin, DNA cleavage, and the peroxidation of RBC membrane by a nonenzymatic Fe3+/O2/thiol mixed-function oxidation system capable of generating hydroxyl radical. These observations suggest that HRPRP could act as a new type of antioxidant protein to maintain the RBC integrity by scavenging reactive oxygen species.