title: Differential stimulation of the GTPase activity of G-proteins by polylysine.
abstract: Polylysine, polyornithine and, to a lesser extent, polyarginine were found to stimulate the GTPase activity of the purified recombinant alpha subunit of the human G(i)-3 transducing protein alpha i-3. Optimal stimulation of 4- to 5-fold was obtained with polylysine concentrations between 1 and 20 microM, higher concentrations being inhibitory. Polylysine at similar concentrations stimulated by 50% the GTPase of transducin (GT), the vision transducing protein, but had only a very slight effect on the GTPase of the p21 product of the H-ras protooncogene. The stimulation of the alpha i-3 GTPase caused by polylysine was due to a reduction of the apparent Km for GTP from 3.8 to 1.3 microM. The stimulation by polylysine was observed at free Mg2+ concentrations below 1 microM. These results indicate that polylysine acts in a fashion similar to mastoparan and substance P in mimicking the action of an agonist-bound receptor on G-proteins.
authors.affiliation: Departamento de Bioquímica, Facultad de Medicina, Universidad de Chile, Santiago.
authors.forename: M
authors.initials: M
authors.lastname: Antonelli
authors.forename: J
authors.initials: J
authors.lastname: Olate
authors.forename: R
authors.initials: R
authors.lastname: Graf
authors.forename: C C
authors.initials: CC
authors.lastname: Allende
authors.forename: J E
authors.initials: JE
authors.lastname: Allende
mesh_terms: D004789:Enzyme Activation / Q000187:drug effects; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006801:Humans; D008274:Magnesium / Q000494:pharmacology; D011107:Polylysine / Q000494:pharmacology*; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D015293:Transducin / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D011107:Polylysine; D006160:Guanosine Triphosphate; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D015293:Transducin; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras); D008274:Magnesium