Ras2
Ras2 is a Saccharomyces cerevisiae guanine nucleotide-binding protein (encoded by the RAS2 gene) which becomes activated by binding GTP when glucose is present in the environment. It affects growth regulation and starvation response.[1]
Modifications
Ras2 becomes post-translationally modified in two ways, both being necessary for its activity: Upon activation, palmitoylation at its C terminus takes place and causes attachment from the cytoplasm to the plasma membrane. Farnesylation allows for efficient interaction with the downstream adenylate cyclase Cyr1p.[2] In wild-type yeast deactivated Ras2 is transported to and degraded in the vacuole, a process for which Whi2 is essential. Interestingly, disturbing this process leads to Ras2 accumulation at the mitochondrial membrane, a behavior that was not observed before.[3]
Ras2-cAMP-PKA pathway
When activating the adenylate cyclase, Ras2 indirectly raises the cellular cAMP levels, thereby activating the PKA, by which in turn it is downregulated.[4]
Downstream effects
In a probably indirect manner via the above PKA regulation, Ras2 has a suppressing effect on the yeast general stress response transcription factor Msn2.[5]
Active Ras2 was also found in the nucleus, the reason is currently unknown.[citation needed]
References
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