Dual function of Ras in Raf activation

Development ◽  
1998 ◽  
Vol 125 (24) ◽  
pp. 4999-5008 ◽  
Author(s):  
W. Li ◽  
M. Melnick ◽  
N. Perrimon
Keyword(s):  
Plasma Membrane ◽  
Nucleotide Binding ◽  
Dual Function ◽  
Guanine Nucleotide ◽  
Guanine Nucleotide Binding Protein ◽  
Raf Kinase ◽  
P21 Ras ◽  
Guanine Nucleotide Binding ◽  
Drosophila Embryos

The small guanine nucleotide binding protein p21(Ras) plays an important role in the activation of the Raf kinase. However, the precise mechanism by which Raf is activated remains unclear. It has been proposed that the sole function of p21(Ras)in Raf activation is to recruit Raf to the plasma membrane. We have used Drosophila embryos to examine the mechanism of Raf (Draf) activation in the complete absence of p21(Ras) (Ras1). We demonstrate that the role of Ras1 in Draf activation is not limited to the translocation of Draf to the membrane through a Ras1-Draf association. In addition, Ras1 is essential for the activation of an additional factor which in turn activates Draf.

scholarly journals The role of a guanine nucleotide-binding protein in the activation of rat liver plasma-membrane adenylate cyclase by forskolin

1983 ◽  
Vol 216 (3) ◽  
pp. 753-759 ◽  
Author(s):  
S K F Wong ◽  
B R Martin
Keyword(s):  
Plasma Membrane ◽  
Adenylate Cyclase ◽  
G Protein ◽  
Rat Liver ◽  
Guanine Nucleotide ◽  
Guanine Nucleotide Binding Protein ◽  
Liver Plasma Membrane ◽  
Guanine Nucleotide Binding ◽  
The Individual

The effects of the photoreactive GTP analogue GTP-gamma-azidoanilide on rat liver plasma-membrane adenylate cyclase are described. U.v. irradiation in the presence of the analogue abolished activation by any effector or combination of effectors that function via the activatory G protein. Partial protection against this inhibition was given by F- and guanosine 5′-[gamma-thio]triphosphate. It is concluded that GTP-gamma-azidoanilide acts by a light-induced covalent reaction with the G protein. In the dark the effects of the analogue were similar to those of GTP. Irradiation in the presence of GTP-gamma-azidoanilide was found to reduce but not to abolish activation of rat liver plasma membrane adenylate cyclase by forskolin. The activation by forskolin and GTP together were greater than the sum of the individual activations. Forskolin doubled adenylate cyclase activity in the presence of glucagon and guanosine 5′-[beta, gamma-imido]triphosphate, which might be expected to activate to the maximum possible extent via the G protein. It is concluded that there are two components to the forskolin activation, a guanine nucleotide-dependent and a guanine nucleotide-independent component.

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