Hemoxidation and binding of the 46-kDa cystalysin of Treponema denticola leads to a cysteine-dependent hemolysis of human erythrocytes

Cystalysin, a 46-kDa protein isolated from the cytosol of Treponema denticola, was capable of both cysteine dependent hemoxidation and hemolysis of human and sheep red blood cells. The activities were characteristic of a cysteine desulfhydrase. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western immunoblotting analysis of the interaction of cystalysin with the red blood cells revealed an interaction of the protein with the red blood cell membrane. Substrates for the enzyme (including L-cysteine and β-chloroalanine) enhanced the interaction, which occurred with both whole red blood cells as well as with isolated and purified red blood cell ghosts. SDS-PAGE and western immunoblotting employing anti-hemoglobin serum revealed that, during the hemoxidative events, the hemoglobin molecule associated with the red blood cell membrane, forming putative Heinz bodies. Spectrophotometric analysis of the hemoxidative events (cystalysin+cysteine+red blood cells) revealed a chemical modification of the native hemoglobin to sulfhemoglobin and methemoglobin. Hemoxidation also resulted in the degradation of both the red blood cell α- and β-spectrin. The results presented suggest that the interaction of cystalysin with the red blood cell membrane results in the chemical oxidation of the hemoglobin molecule as well as an alteration in the red blood cell membrane itself.