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Figure 3.
Figure 3 Model for the GDI-mediated Rab/Ypt interaction with the
putative Rab receptors and membranes. (A) GDI-mediated delivery
of prenylated RabGTPases to the membrane is proposed to involve
docking of the Rab:GDI complex with a putative membrane Rab
recruitment/GDF via a protein:protein interaction (2). The
docked complex undergoes a conformational change, which leads to
the transfer of the first and then the second geranylgeranyl
moiety into the membrane and subsequently to the release of the
Rab C-terminus from the CBR (3 and 4). Finally, GDI is released
into the cytosol and the Rab protein enters its functional
cycle. (B) GDI-mediated extraction of prenylated RabGTPases from
the membrane. Initial recognition is mediated by the
low-affinity interaction of the Rab-binding platform with the
CBR of GDI (7). This leads to the positioning of GDI domain II
on the lipid bilayer over the buried geranylgeranyl moieties of
the Rab protein (8). The geranylgeranyl lipids are transferred
from the membrane to the lipid binding sites on GDI in two
consecutive steps (9 and 10), leading to dissociation of the
complex from membrane (11).
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