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Molecular and Cellular Biology, September 1999, p. 6297-6305, Vol. 19, No. 9
Max-Planck-Institut für Molekulare
Physiologie, 44227 Dortmund, Germany
Received 13 October 1998/Returned for modification 2 December
1998/Accepted 17 June 1999
The introduction of mutation D119N (or its homolog) in the NKxD
nucleotide binding motif of various Ras-like proteins produces constitutively activated or dominant-negative effects, depending on the
system and assay. Here we show that Ras(D119N) has an inhibitory effect
at a cell-specific concentration in PC12 and NIH 3T3 cells. Biochemical
data strongly suggest that the predominant effect of mutation D119N in
Ras
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Copyright © 1999, American Society for Microbiology. All rights reserved.
The Ras Mutant D119N Is Both Dominant Negative and
Activated

a strong decrease in nucleotide affinity
enables this mutant (i)
to sequester its guanine nucleotide exchange factor, as well as (ii) to
rapidly bind GTP, independent of the regulatory action of the exchange
factor. Since mutation D119N does not affect the interaction between
Ras and effector molecules, the latter effect causes Ras(D119N) to act
as an activated Ras protein at concentrations higher than that of the
exchange factor. In comparison, Ras(S17N), which also shows a strongly
decreased nucleotide affinity, does not bind to effector molecules.
These results point to two important prerequisites of dominant-negative
Ras mutants: an increased relative affinity of the mutated Ras for the
exchange factor over that for the nucleotide and an inability to
interact with the effector or effectors. Remarkably, the introduction
of a second, partial-loss-of-function, mutation turns Ras(D119N) into a
strong dominant-negative mutant even at high concentrations, as
demonstrated by the inhibitory effects of Ras(E37G/D119N) on nerve
growth factor-mediated neurite outgrowth in PC12 cells and
Ras(T35S/D119N) on fetal calf serum-mediated DNA synthesis in NIH 3T3
cells. Interpretations of these results are discussed.
*
Corresponding author. Present address: Werkgroep
Moleculaire Microbiologie, Rijksuniversiteit Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands. Phone: 31 50 363 2158. Fax: 31 50 363 2154. E-mail: r.h.cool{at}biol.rug.nl.
Present address: Institut für Pharmakologie und Toxikologie
der Albert-Ludwigs-Universität, 79104 Freiburg, Germany.
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