scholarly journals Characterization by two-dimensional peptide mapping of the gamma subunits of Ns and Ni, the regulatory proteins of adenylyl cyclase, and of transducin, the guanine nucleotide-binding protein of rod outer segments of the eye.

1985 ◽  
Vol 260 (27) ◽  
pp. 14867-14872 ◽  
Author(s):  
J D Hildebrandt ◽  
J Codina ◽  
W Rosenthal ◽  
L Birnbaumer ◽  
E J Neer ◽  
...  
Keyword(s):  
Adenylyl Cyclase ◽  
Peptide Mapping ◽  
Nucleotide Binding ◽  
Regulatory Proteins ◽  
Rod Outer Segments ◽  
Guanine Nucleotide ◽  
Two Dimensional ◽  
Guanine Nucleotide Binding Protein ◽  
Gamma Subunits ◽  
Guanine Nucleotide Binding

Hepatocyte beta-adrenergic responsiveness and guanine nucleotide-binding regulatory proteins

1989 ◽  
Vol 256 (2) ◽  
pp. C384-C389 ◽  
Author(s):  
J. A. Garcia-Sainz ◽  
M. E. Huerta-Bahena ◽  
C. C. Malbon
Keyword(s):  
Binding Protein ◽  
Nucleotide Binding ◽  
Regulatory Proteins ◽  
Guanine Nucleotide ◽  
Guanine Nucleotide Binding Protein ◽  
Beta Adrenergic ◽  
Adp Ribosylation ◽  
Liver Membranes ◽  
Guanine Nucleotide Binding ◽  
Nucleotide Binding Protein

Hepatocytes isolated from hypothyroid, adrenalectomized, or partially hepatectomized rats display an enhanced beta-adrenergic responsiveness as compared with cells from control animals. The enhanced beta-adrenergic responsiveness is evidenced by both increased ureagenesis and adenosine 3',5'-cyclic monophosphate (cAMP) accumulation in response to isoproterenol. The role of stimulatory guanine nucleotide-binding protein (Gs) and inhibitory guanine nucleotide-binding protein (Gi) in the enhanced responsiveness was studied. It was observed, contrary to what would have been anticipated, that the level of Gs [as reflected by cholera toxin-catalyzed ADP ribosylation, 5'-guanosine gamma-thiotriphosphate (GTP gamma S)-stimulated adenylate cyclase activity, and a functional reconstitution assay] was decreased in liver membranes from adrenalectomized and partially hepatectomized rats as compared with the controls. Furthermore, the level of Gi was increased in these conditions as reflected by pertussis toxin-catalyzed ADP ribosylation. The data suggest that changes in beta-adrenergic receptor levels rather than the levels of guanine nucleotide-binding (G) regulatory proteins predominate in regulation of hepatic beta-adrenergic responses by hypothyroidism, adrenalectomy, or partial hepatectomy.

scholarly journals Influence of gamma subunit prenylation on association of guanine nucleotide-binding regulatory proteins with membranes.

1992 ◽  
Vol 3 (1) ◽  
pp. 49-61 ◽  
Author(s):  
K H Muntz ◽  
P C Sternweis ◽  
A G Gilman ◽  
S M Mumby
Keyword(s):  
Membrane Fraction ◽  
Plasma Membranes ◽  
Nucleotide Binding ◽  
Site Directed Mutagenesis ◽  
Regulatory Proteins ◽  
Guanine Nucleotide ◽  
Gamma Subunit ◽  
Cos Cells ◽  
Gamma Subunits ◽  
Guanine Nucleotide Binding

Two approaches were taken to address the possible role of gamma-subunit prenylation in dictating the cellular distribution of guanine nucleotide-binding regulatory proteins. Prenylation of gamma subunits was prevented by site-directed mutagenesis or by inhibiting the synthesis of mevalonate, the precursor of cellular isoprenoids. When beta or gamma subunits were transiently expressed in COS-M6 simian kidney cells (COS) cells, the proteins were found in the membrane fraction by immunoblotting. Immunofluorescence experiments indicated that the proteins were distributed to intracellular structures in addition to plasma membranes. Replacement of Cys68 of gamma with Ser prevented prenylation of the mutant protein and association of the protein with the membrane fraction of COS cells. Immunoblotting results demonstrated that some of the beta subunits were found in the cytoplasm when coexpressed with the nonprenylated mutant gamma subunit. When Neuro 2A cells were treated with compactin to inhibit protein prenylation, a fraction of endogenous beta and gamma was distributed in the cytoplasm. It is concluded that prenylation facilitates association of gamma subunits with membranes, that the cellular location of gamma influences the distribution of beta, and that prenylation is not an absolute requirement for interaction of beta and gamma.

scholarly journals GTP analogues promote release of the α subunit of the guanine nucleotide binding protein, Gi2, from membranes of rat glioma C6 BU1 cells

1988 ◽  
Vol 254 (2) ◽  
pp. 391-396 ◽  
Author(s):  
G Milligan ◽  
I Mullaney ◽  
C G Unson ◽  
L Marshall ◽  
A M Spiegel ◽  
...  
Keyword(s):  
G Protein ◽  
Pertussis Toxin ◽  
Nucleotide Binding ◽  
Alpha Subunit ◽  
Guanine Nucleotide ◽  
Guanine Nucleotide Binding Protein ◽  
Rat Glioma ◽  
Glioma C6 ◽  
Gamma Subunits ◽  
Guanine Nucleotide Binding

The major pertussis-toxin-sensitive guanine nucleotide-binding protein of rat glioma C6 BU1 cells corresponded immunologically to Gi2. Antibodies which recognize the alpha subunit of this protein indicated that it has an apparent molecular mass of 40 kDa and a pI of 5.7. Incubation of membranes of these cells with guanosine 5′-[beta gamma-imido]triphosphate, or other analogues of GTP, caused release of this polypeptide from the membrane in a time-dependent manner. Analogues of GDP or of ATP did not mimic this effect. The GTP analogues similarly caused release of the alpha subunit of Gi2 from membranes of C6 cells in which this G-protein had been inactivated by pretreatment with pertussis toxin. The beta subunit was not released from the membrane under any of these conditions, indicating that the release process was a specific response to the dissociation of the G-protein after binding of the GTP analogue. Similar nucleotide profiles for release of the alpha subunits of forms of Gi were noted for membranes of both the neuroblastoma x glioma hybrid cell line NG108-15 and of human platelets. These data provide evidence that: (1) pertussis-toxin-sensitive G-proteins, in native membranes, do indeed dissociate into alpha and beta gamma subunits upon activation; (2) the alpha subunit of ‘Gi-like’ proteins need not always remain in intimate association with the plasma membrane; and (3) the alpha subunit of Gi2 can still dissociate from the beta/gamma subunits after pertussis-toxin-catalysed ADP-ribosylation.

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