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Mol. Cell. Biol., Aug 1995, 4578-4584, Vol 15, No. 8
SB Cantor, T Urano and LA Feig
Ral proteins constitute a distinct family of Ras-related GTPases. Although
similar to Ras in amino acid sequence, Ral proteins are activated by a
unique nucleotide exchange factor and inactivated by a distinct
GTPase-activating protein. Unlike Ras, they fail to promote transformed
foci when activated versions are expressed in cells. To identify downstream
targets that might mediate a Ral-specific function, we used a Saccharomyces
cerevisiae-based interaction assay to clone a novel cDNA that encodes a
Ral-binding protein (RalBP1). RalBP1 binds specifically to the active
GTP-bound form of RalA and not to a mutant Ral with a point mutation in its
putative effector domain. In addition to a Ral-binding domain, RalBP1 also
contains a Rho-GTPase-activating protein domain that interacts
preferentially with Rho family member CDC42. Since CDC42 has been
implicated in bud site selection in S. cerevisiae and filopodium formation
in mammalian cells, Ral may function to modulate the actin cytoskeleton
through its interactions with RalBP1.
Copyright © 1995, American Society for Microbiology
Identification and characterization of Ral-binding protein 1, a potential downstream target of Ral GTPases
Department of Biochemistry, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
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