Weonmee Park

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Millions of people worldwide suffer from nutritional imbalances of essential metals like zinc. These same metals, along with pollutants like cadmium and lead, contaminate soils at many sites around the world. In addition to posing a threat to human health, these metals can poison plants, livestock, and wildlife. Deciphering how metals are absorbed,(More)
Growth factor-triggered activation of Ras proteins is believed to be mediated by guanine nucleotide exchange factors (CDC25/GRF and SOS1/2) that promote formation of the active Ras GTP-bound state. Although the mechanism(s) of guanine nucleotide exchange factor regulation is unclear, recent studies suggest that translocation of SOS1 to the plasma membrane,(More)
Previously we found that negatively charged residues at positions 62, 63, and 69 of H-Ras are involved in binding to the CDC25 guanine nucleotide exchange factor (GEF). Using site-directed mutagenesis, we have changed conserved, positively charged residues of CDC25GEF to glutamic acid. We find the nonfunctional CDC25R1374E mutant and the nonfunctional(More)
Ras proteins bound to GDP are biologically inactive while those bound to GTP are active. Ras-specific guanine nucleotide-exchange factors (GEFs) have been shown to activate Ras proteins. We used oligodeoxyribonucleotide primers with sequences similar to the cDNAs of rat and mouse cdc25 (encoding a Ras-GEF) to amplify, by the PCR, sequences with the(More)
Our results demonstrate that the GAL4 two-hybrid system can be useful for studying interactions of the wild-type and mutant forms of Ras proteins with the CDC25 guanine nucleotide exchange factor (CDC25-GEF). In addition, our findings show that a negative result in the GAL4 two-hybrid system does not indicate that the two proteins tested do not interact(More)
In previous studies we changed five conserved amino acid residues in the catalytic domain of the yeast Ras-specific guanine nucleotide exchange factor CDC25GEF (Park et al., 1994). One of the substitutions (R1489E) resulted in a molecule which could bind Ras but was catalytically inactive. These observations suggested that CDC25R1489E might be a(More)
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