Yrb1p interaction with the gsp1p C terminus blocks Mog1p stimulation of GTP release from Gsp1p.
Mog1p, a multicopy suppressor of gsp1, the temperature-sensitive mutant of the Saccharomyces cerevisiae Ran homologue, binds to GTP-Gsp1p but not to GDP-Gsp1p. The function of Mog1p in the Ran cycle is as yet unknown. This study found that Mog1p releases a nucleotide from GTP-Gsp1p but not from GDP-Gsp1p. Yrb1p, the S. cerevisiae homologue of RanBP1, which is a strong inhibitor of RCC1-stimulated nucleotide release, also inhibited the Mog1p- stimulated nucleotide release from GTP-Gsp1p. At a concentration corresponding to the molar concentration of GTP-Gsp1p, Yrb1p completely inhibited the Mog1p-stimulated nucleotide release. Consistently, the Yrb1p.GTP-Gsp1p complex was more stable than the Mog1p.GTP-Gsp1p complex. Yrb1p did not inhibit the Mog1p-stimulated nucleotide release from GTP-Gsp1DeltaC. The Gsp1DeltaC protein lacks the final eight amino acids of the C terminus, and for this reason, the interaction between GTP-Gsp1DeltaC and Yrb1p was strongly reduced. On the other hand, Mog1p binds to GTP-Gsp1DeltaC more efficiently than to GTP-Gsp1p.[1]References
- Yrb1p interaction with the gsp1p C terminus blocks Mog1p stimulation of GTP release from Gsp1p. Oki, M., Nishimoto, T. J. Biol. Chem. (2000) [Pubmed]
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