title: Characterization of a Gi-protein from Trypanosoma cruzi epimastigote membranes.
abstract: A guanosine 5'-[gamma-[35S]thio]triphosphate-binding activity was detergent-extracted from Trypanosoma cruzi membranes. This binding activity was co-eluted from gel-filtration columns with a factor which, in a heterologous reconstitution system, blocks glucagon stimulation of adenylate cyclase activity in liver membranes. ADP-ribosylation of these membranes by pertussis toxin eliminated this blocking capacity. Incubation of T. cruzi membranes with activated pertussis toxin and [adenylate-32P]NAD+ led to the incorporation of radioactivity into a labelled product with an apparent M(r) of approx. 43,000. Crude membranes were electrophoresed on SDS/polyacrylamide gels and analysed, by Western blotting, with GA/1 anti-alpha common, AS/7 anti-alpha t, anti-alpha i1 and anti-alpha i2 polyclonal antibodies. These procedures led to the identification of a specific polypeptide band of about 43 kDa. Another polypeptide reacting with the SW/1 anti-beta antibody, of about 30 kDa, was also detected in the membrane fraction.
authors.affiliation: Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Buenos Aires, Argentina.
authors.forename: O A
authors.initials: OA
authors.lastname: Coso
authors.forename: A
authors.initials: A
authors.lastname: Díaz Añel
authors.forename: H
authors.initials: H
authors.lastname: Martinetto
authors.forename: J P
authors.initials: JP
authors.lastname: Muschietti
authors.forename: M
authors.initials: M
authors.lastname: Kazanietz
authors.forename: D
authors.initials: D
authors.lastname: Fraidenraich
authors.forename: H N
authors.initials: HN
authors.lastname: Torres
authors.forename: M M
authors.initials: MM
authors.lastname: Flawia
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D037361:Adenylate Cyclase Toxin; D000595:Amino Acid Sequence; D000818:Animals; D019204:GTP-Binding Proteins / Q000032:analysis / Q000276:immunology / Q000502:physiology*; D006160:Guanosine Triphosphate / Q000378:metabolism; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000032:analysis / Q000276:immunology / Q000502:physiology; D008969:Molecular Sequence Data; D037342:Pertussis Toxin; D015800:Protozoan Proteins / Q000032:analysis* / Q000276:immunology; D013462:Sulfur Radioisotopes; D014349:Trypanosoma cruzi / Q000737:chemistry* / Q000502:physiology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D037361:Adenylate Cyclase Toxin; D046911:Macromolecular Substances; D008565:Membrane Proteins; D015800:Protozoan Proteins; D013462:Sulfur Radioisotopes; D010566:Virulence Factors, Bordetella; D000244:Adenosine Diphosphate; D006160:Guanosine Triphosphate; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins