title: ADP-ribosylation of bovine S-antigen by cholera toxin.
abstract: The S-antigen (alias 48K protein or arrestin) of bovine rod photoreceptors contains two stretches of amino acid sequence homologous to the ADP-ribosylation sites of the alpha subunit of transducin (Ta). We have found that cholera toxin transfers the ADP-ribosyl group from NAD to purified bovine S-antigen as well as to S-antigen in rod outer segment membranes, while Bordetella pertussis toxin is unable to catalyze the transfer reaction efficiently. Under the same conditions, both toxins catalyzed ADP-ribosylation of Ta in rod outer segments. The ADP-ribosylation of S-antigen by cholera toxin indicates that S-antigen not only exhibits sequence homology with the ADP-ribosylation sites of Ta, but it must also resemble Ta in the tertiary structure of the domain which determines the susceptibility of S-antigen to the catalytic action of cholera toxin. These results suggest that S-antigen may function as a competitor of Ta in some stage of the cGMP cascade of visual transduction.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City 73190.
authors.forename: N
authors.initials: N
authors.lastname: Komori
authors.forename: M A
authors.initials: MA
authors.lastname: Rider
authors.forename: D J
authors.initials: DJ
authors.lastname: Takemoto
authors.forename: H
authors.initials: H
authors.lastname: Shichi
authors.forename: H
authors.initials: H
authors.lastname: Matsumoto
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D000818:Animals; D000941:Antigens / Q000032:analysis / Q000378:metabolism*; D019393:Arrestin; D001665:Binding Sites; D001666:Binding Sites, Antibody / Q000187:drug effects; D002417:Cattle; D002772:Cholera Toxin / Q000494:pharmacology*; D005136:Eye Proteins / Q000032:analysis / Q000378:metabolism*; D037342:Pertussis Toxin; D010786:Photoreceptor Cells / Q000032:analysis / Q000378:metabolism; D015293:Transducin / Q000276:immunology / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D000941:Antigens; D019393:Arrestin; D005136:Eye Proteins; D010566:Virulence Factors, Bordetella; D000246:Adenosine Diphosphate Ribose; D002772:Cholera Toxin; D037342:Pertussis Toxin; D015293:Transducin