Gek binds specifically to Dcdc42.
(a) Summary of two-hybrid interactions of Gek (clone
c17, see Fig. 2a) with various GTPase baits.
Interactions were assayed both for the ability to produce
His+ colonies on triple selection plates, and for
β-galactosidase activity, of yeast cells containing both plasmids
(13). None of the GTPase fusion proteins interacted with the activation
domain alone. (b) Binding of in
vitro-translated full-length Gek wild-type (lanes 1–4) or
GekΔISP bearing a three amino acid deletion (see Fig.
2e) in the Cdc42 binding domain (lanes 5–8) to various
glutathione S-transferase-GTPases fusion proteins shown
at the bottom of the figure. Only activated form of Dcdc42 (Dcdc42V12)
can bind to wild-type Gek (lane 3). Mutations in the effector domain
(A35) of Dcdc42 (lane 4) or in the Cdc42 binding domain of Gek (lanes 7
and 8) disrupt the binding. Drac1 does not bind to Gek (lanes 1, 2, 5,
and 6). The arrow indicates the largest translation product of Gek,
which matches the predicted molecular mass of 184 kDa.