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

• Overexpression of Bud5p can suppress mutations in the Gsp1p guanine nucleotide exchange factor Prp20p in Saccharomyces cerevisiae [8].

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].

References