scholarly journals Current Topics in Heterotrimeric GTP-binding Proteins. Structure and function of heterotrimeric G-proteins.

1994 ◽  
Vol 103 (6) ◽  
pp. 249-262 ◽  
Author(s):  
Shinichi HOSHINO ◽  
Toshiaki KATADA
Keyword(s):  
G Proteins ◽  
Binding Proteins ◽  
Structure And Function ◽  
Heterotrimeric G Proteins ◽  
Gtp Binding Proteins ◽  
Gtp Binding ◽  
And Function

Mutational analysis of the structure and function of GTP-binding proteins

1990 ◽  
Vol 30 ◽  
pp. 75-87 ◽  
Author(s):  
Susan B. Masters ◽  
Claudia A. Landis ◽  
Henry R. Bourne
Keyword(s):  
Binding Proteins ◽  
Mutational Analysis ◽  
Structure And Function ◽  
Gtp Binding Proteins ◽  
Gtp Binding ◽  
And Function

Structure and Function of Signal-Transducing GTP-Binding Proteins

1991 ◽  
Vol 60 (1) ◽  
pp. 349-400 ◽  
Author(s):  
Yoshito Kaziro ◽  
Hiroshi Itoh ◽  
Tohru Kozasa ◽  
Masato Nakafuku ◽  
Takaya Satoh
Keyword(s):  
Binding Proteins ◽  
Structure And Function ◽  
Gtp Binding Proteins ◽  
Gtp Binding ◽  
And Function

scholarly journals Characterization of GTP-binding proteins in Golgi-associated membrane vesicles from rat adipocytes

1992 ◽  
Vol 283 (3) ◽  
pp. 795-801 ◽  
Author(s):  
A Schürmann ◽  
W Rosenthal ◽  
G Schultz ◽  
H G Joost
Keyword(s):  
G Proteins ◽  
Glucose Transport ◽  
Subcellular Distribution ◽  
Sucrose Gradient ◽  
Binding Proteins ◽  
Glucose Transporters ◽  
Beta Subunits ◽  
Transport Activity ◽  
Gtp Binding Proteins ◽  
Gtp Binding

We have previously reported that guanine nucleotides inhibit glucose transport activity reconstituted from adipocyte membrane fractions. In order to further investigate the hypothetical involvement of guanine-nucleotide-binding proteins (GTP-binding proteins) in the regulation of insulin-sensitive glucose transport activity, we studied their subcellular distribution in adipocytes treated or not with insulin. Adipocytes were homogenized and fractionated to yield plasma membranes (PM) and a Golgi-enriched fraction of intracellular membranes (low-density microsomes, LDM). In these membrane fractions, total guanosine 5′-[gamma-[35S]thio]triphosphate ([35S]GTP[S]) binding, alpha- and beta-subunits of heterotrimeric G-proteins, proto-oncogenes Ha-ras and K-ras, and 23-28 kDa GTP-binding proteins were assayed. The levels of alpha s and alpha i (the alpha-subunits of Gs and Gi) were approx. 8-fold lower in LDM than in PM; beta-subunits, Ha-ras and K-ras were not detectable in LDM. Total GTP[S]-binding sites and 23-28 kDa GTP-binding proteins were present in LDM in approximately the same concentrations as in PM. Insulin gave rise to the characteristic translocation of glucose transporters, but failed to alter the subcellular distribution of any of the GTP-binding proteins. Fractionation of the LDM on a discontinuous sucrose gradient revealed that alpha s and alpha i, as detected with antiserum against a common peptide sequence (alpha common), and the bulk of the 23-28 kDa G-proteins sedimented at different sucrose densities. None of the GTP-binding proteins co-sedimented with glucose transporters. Furthermore, the inhibitory effect of GTP[S] on the reconstituted transport activity was lost in the peak fractions of glucose transporters partially purified on the sucrose gradient. These data indicate that LDM from adipocytes contain several GTP-binding proteins in discrete vesicle populations. However, the intracellular GTP-binding proteins are not tightly associated with the vesicles containing the glucose transporter.

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