Molecular heterogeneity of the subclasses of islet-activating protein (pertussis toxin)-sensitive GTP-binding proteins in porcine thyroid tissue.
From porcine thyroid cell membranes, we purified five GTP-binding proteins (G-proteins); Nos. 1 to 3 have 41-kDa alpha-subunits, and Nos. 4 and 5 have 40-kDa alpha-subunits. They were chromatographically (Mono Q) separable and served as specific substrates for islet-activating protein (pertussis toxin). G-proteins 1 and 2 were indistinguishable from porcine brain Gi1 with respect to three criteria, i.e., mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), pI of the ADP-ribosylated alpha-subunit, and immunoreactivity. G-protein 3 was identified as Gi3 by immunoreactivity. The SDS-PAGE and isoelectric focusing (IEF) analyses identified G-proteins 4 and 5 as being chromatographically heterogeneous subtypes of Gi2 in comparison with a pure porcine brain preparation. The IEF analysis also disclosed that each of the Gi1, Gi2, and Gi3 subspecies isolated in the present study has a minor component characterized by a slightly lower pI of its alpha-subunit. We conclude that porcine thyroid tissue contains at least Gi1, Gi2, and Gi3, and that each is made up of heterogeneous populations.
Sato
K
K
Department of Physical Biochemistry, Gunma University, Maebashi, Japan.
Okajima
F
F
Katada
T
T
Kondo
Y
Y
D000818:Animals; D001792:Blood Platelets / Q000032:analysis; D004591:Electrophoresis, Polyacrylamide Gel; D004910:Erythrocyte Membrane / Q000032:analysis; D019204:GTP-Binding Proteins / Q000145:classification* / Q000302:isolation & purification; D006801:Humans; D015151:Immunoblotting; D007525:Isoelectric Focusing; D037342:Pertussis Toxin; D013268:Stimulation, Chemical; D013552:Swine; D013961:Thyroid Gland / Q000032:analysis*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D010566:Virulence Factors, Bordetella; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins