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Gene Review

BUD5  -  Bud5p

Saccharomyces cerevisiae S288c

Synonyms: Bud site selection protein 5, YCR038C, YCR38C, YCR526
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High impact information on BUD5

  • The BUD5 nucleotide sequence predicts a protein of 538 amino acids that has similarity to the S. cerevisiae CDC25 product, an activator of RAS proteins that catalyzes GDP-GTP exchange [1].
  • We also show that BUD5 interacts functionally with a gene, BEM1, that is required for bud formation [1].
  • Although overexpressed BUD5 cannot substitute for CDC25 function, we present evidence that its gene product can bind to the guanine nucleotide binding-deficient RAS2val19ala22 gene product and thereby counteract its dominant-negative effect [2].
  • Mutants defective in BUD1, BUD2 or BUD5 choose bud sites randomly [3].
  • Bud5 also physically interacts with Axl2/Bud10, a transmembrane glycoprotein, suggesting that a receptor-like transmembrane protein recruits a GDP/GTP exchange factor to connect an intrinsic spatial signal to oriented cell growth [4].

Biological context of BUD5

  • Finally, we found a new start codon of BUD5, which extends the open reading frame to 210 bp upstream of the previously estimated start site, thus encoding a polypeptide of 608 amino acid residues [5].
  • These bipolar-specific mutations of BUD5 disrupted proper localization of Bud5p in diploid a/alpha cells without affecting Bud5p localization in haploid alpha cells [5].
  • We found that Bud5 is localized at the cell division site and the presumptive bud site [4].
  • In the budding yeast Saccharomyces cerevisiae, the Ras-like GTPase Bud1/Rsr1 and its guanosine 5'-diphosphate (GDP)/guanosine 5'-triphosphate (GTP) exchange factor Bud5 are involved in the selection of a specific site for growth, thus determining cell polarity [4].
  • In haploids, Bud5 forms double rings that encircle the mother-bud neck and split upon cytokinesis so that each progeny cell inherits Bud5 at the axial division remnant [6].

Anatomical context of BUD5

  • Like Ras, Bud1p GTPase is constitutively associated with the plasma membrane; however, concentrated activities of Bud5p GDP-GTP exchange factor and Bud2p GTPase-activating protein at the future bud site promote rapid cycling of Bud1p between GTP- and GDP-bound conformations in a spatially restricted manner [7].

Associations of BUD5 with chemical compounds


Physical interactions of BUD5

  • Bud5p with these additional N-terminal residues interacted with Bud8p, a potential bipolar landmark, suggesting that the N-terminal region is necessary for recognition of the spatial cues [5].

Other interactions of BUD5

  • In contrast, similar chimeras made between CDC25 and BUD5 lead to proteins that are inactive both in the Ras and budding control pathways [9].
  • These,findings raise the possibility that Bud5p could act as a cytoplasmic exchange factor for Gsp1p and, therefore, that a complete GDP/GTP cycle could take place in the cytoplasm [8].
  • The region required for full biological activity is approximately 450 residues and contains two segments homologous to other proteins: one found in both Ras-specific exchange factors and the more distant Bud5 and Lte1 proteins, and a smaller segment of 48 amino acids found only in the Ras-specific exchange factors [10].
  • We examined the localizations of Bud5 and Bud2 [6].
  • Consistent with such a role, Axl1 associated biochemically with Bud4 and Bud5 [11].


  1. Yeast BUD5, encoding a putative GDP-GTP exchange factor, is necessary for bud site selection and interacts with bud formation gene BEM1. Chant, J., Corrado, K., Pringle, J.R., Herskowitz, I. Cell (1991) [Pubmed]
  2. Functional cloning of BUD5, a CDC25-related gene from S. cerevisiae that can suppress a dominant-negative RAS2 mutant. Powers, S., Gonzales, E., Christensen, T., Cubert, J., Broek, D. Cell (1991) [Pubmed]
  3. BUD2 encodes a GTPase-activating protein for Bud1/Rsr1 necessary for proper bud-site selection in yeast. Park, H.O., Chant, J., Herskowitz, I. Nature (1993) [Pubmed]
  4. A GDP/GTP exchange factor involved in linking a spatial landmark to cell polarity. Kang, P.J., Sanson, A., Lee, B., Park, H.O. Science (2001) [Pubmed]
  5. Specific residues of the GDP/GTP exchange factor Bud5p are involved in establishment of the cell type-specific budding pattern in yeast. Kang, P.J., Lee, B., Park, H.O. J. Biol. Chem. (2004) [Pubmed]
  6. A localized GTPase exchange factor, Bud5, determines the orientation of division axes in yeast. Marston, A.L., Chen, T., Yang, M.C., Belhumeur, P., Chant, J. Curr. Biol. (2001) [Pubmed]
  7. A mechanism of Bud1p GTPase action suggested by mutational analysis and immunolocalization. Michelitch, M., Chant, J. Curr. Biol. (1996) [Pubmed]
  8. Overexpression of Bud5p can suppress mutations in the Gsp1p guanine nucleotide exchange factor Prp20p in Saccharomyces cerevisiae. Clément, M., Lavallée, F., Barbès-Morin, G., de Repentigny, L., Belhumeur, P. Mol. Genet. Genomics (2001) [Pubmed]
  9. Two subclasses of guanine exchange factor (GEF) domains revealed by comparison of activities of chimeric genes constructed from CDC25, SDC25 and BUD5 in Saccharomyces cerevisiae. Camus, C., Boy-Marcotte, E., Jacquet, M. Mol. Gen. Genet. (1994) [Pubmed]
  10. Influence of guanine nucleotides on complex formation between Ras and CDC25 proteins. Lai, C.C., Boguski, M., Broek, D., Powers, S. Mol. Cell. Biol. (1993) [Pubmed]
  11. Subcellular localization of Axl1, the cell type-specific regulator of polarity. Lord, M., Inose, F., Hiroko, T., Hata, T., Fujita, A., Chant, J. Curr. Biol. (2002) [Pubmed]
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