Isolation of a sperm membrane sialoglycoprotein autoantigen from rabbit testes

A single rabbit sperm membrane autoantigen has been isolated from rabbit testes by immunoadsorbent chromatography, agarose chromatography, and electrophoresis. This rabbit sperm autoantigen (RSA-1) is located in the sperm plasma membrane and blocks the sperm cytotoxic (immobilizing) activity of autoantisera. RSA-1 is a sialoglycoprotein, approximately 40% carbohydrate and containing 0.2 micrograms sialic acid/microgram protein. Its m.w. is estimated at 13,000 +/- 1200 by SDA-PAGE. RSA-1 can self-aggregate into higher m.w. forms. Approximately 0.6 mg of RSA-1 can be isolated from 100 rabbits testes. The isolated RSA-1 shows a 300-fold increase in specific cytotoxic (immobilizing) inhibitory activity over the starting testis pellet material.