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Originally published In Press as doi:10.1074/jbc.M000729200 on March 21, 2000
J. Biol. Chem., Vol. 275, Issue 23, 17754-17761, June 9, 2000
Analysis of the Role of the Hypervariable Region of Yeast Ras2p
and Its Farnesylation in the Interaction with Exchange Factors and
Adenylyl Cyclase*
Jean-Bernard
Créchet ,
Eric
Jacquet ,
Alberto
Bernardi§, and
Andrea
Parmeggiani¶
From the Groupe de Biophysique-Equipe 2, Ecole Polytechnique,
F-91128 Palaiseau Cedex, France and the § Populations,
Génétique et Evolution, Unité Propre de Recherche
n° 9034 du Centre Nationale de la Recherche Scientifique,
F-91198 Gif-sur-Yvette, France
Ras proteins from Saccharomyces
cerevisiae differ from mammalian Ha-Ras in their extended
C-terminal hypervariable region. We have analyzed the function of this
region and the effect of its farnesylation with respect to the action
of the GDP/GTP exchange factors (GEFs) Cdc25p and Sdc25p and the target
adenylyl cyclase. Whereas Ras2p farnesylation had no effect on the
interaction with purified GEFs from the Cdc25 family, this modification
became a strict requirement for stimulation of the nucleotide exchange on Ras using reconstituted cell-free systems with GEFs bound to the
cell membrane. Determination of GEF effects showed that in cell
membrane the Cdc25p dependent activity on Ras2p was predominant over
that of Sdc25p. In contrast to full-length GEFs, a membrane-bound C-terminal region containing the catalytic domain of Cdc25p was still
able to react productively with unfarnesylated Ras2p. These results
indicate that in membrane-bound full-length GEF the N-terminal moiety
regulates the interaction between catalytic domain and farnesylated
Ras2p·GDP. Differently from GEF, full activation of adenylyl cyclase
did not require farnesylation of Ras2p·GTP, even if this step of
maturation was found to facilitate the interaction. The use of
Ha-Ras/Ras2p chimaeras of different length emphasized the key role of
the hypervariable region of Ras2p in inducing maximum activation of
adenylyl cyclase and for a productive interaction with membrane-bound
GEF.
*
This work was supported by contracts BIOTECH BIO4-CT96-1110
from the European Community, Ligue Nationale Française Contre le
Cancer, and Association pour la Recherche sur le Cancer Grant 9846.The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement" in
accordance with 18 U.S.C. Section
1734 solely to indicate this fact.
Present address: Dépt. de Chimie, Laboratoire de
Synthèse Organique, Ecole Polytechnique, F-91128 Palaiseau cedex, France.
¶
To whom correspondence should be addressed. Tel.:
33-1-6933-3298; Fax: 33-1-6933-3004; E-mail:
andrea@pmc.polytechnique.fr.
Copyright © 2000 by The American Society for Biochemistry and Molecular Biology, Inc.

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Copyright © 2000 by the American Society for Biochemistry and Molecular Biology.
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