Spermatozoa contain a guanine nucleotide-binding protein ADP-ribosylated by pertussis toxin.

Spermatozoa from invertebrates (sea urchin, starfish) and vertebrates (trout, guinea pig, bull, pig, human) contain a membrane-bound protein that is ADP-ribosylated by pertussis toxin but not by cholera toxin. The Mr of this protein is 39,000 in invertebrate sperm and 41,000 in mammalian sperm, but 40,000 in trout spermatozoa. The pertussis toxin substrate from sea urchin sperm copurified with [gamma-35S]GTP binding activity. Chymotryptic maps of this ADP-ribosylated protein from sea urchin sperm were the same as those of alpha-subunit of Go from rat brain. Antiserum to the beta-subunit of bovine retinal transducin bound to a sperm protein with Mr approximately 35,000. These studies are the first describing a guanine nucleotide-binding coupling protein in sperm.