Fig. 4: Postulated neurofibromin action.
From: The structure of neurofibromin isoform 2 reveals different functional states
a, In the closed state, inactivated Nf1 cannot downregulate Ras. In the active, open Nf1 state, SPRED1 can bring Nf1 to the cell membrane where Nf1 can bind and downregulate monomeric Ras×GTP to Ras×GDP. The open Nf1 state could also regulate a Ras×GTP dimer. b, Hypothetical model of a not-observed Nf1 state with two partially open GRDs that would allow downregulation of one Ras×GTP dimer at the same time in one cycle.
