The small GTPases Ras and Rheb studied by multidimensional NMR spectroscopy: structure and function.

Ras GTPases are key players in cellular signalling because they act as binary switches. These states manifest through toggling between an active (GTP-loaded) and an inactive (GDP-loaded) form. The hydrolysis and replenishing of GTP is controlled by two additional protein classes: GAP (GTPase-activating)- and GEF (Guanine nucleotide exchange factors)-proteins.

Rheb in neuronal degeneration, regeneration, and connectivity.

The small GTPase Rheb was originally detected as an immediate early response protein whose expression was induced by NMDA-dependent synaptic activity in the brain. Rheb's activity is highly regulated by its GTPase activating protein (GAP), the tuberous sclerosis complex protein, which stimulates the conversion from the active, GTP-loaded into the inactive, GDP-loaded conformation. Rheb has been established as an evolutionarily conserved molecular switch protein regulating cellular growth, cell volume, cell cycle, autophagy, and amino acid uptake.