Disease relevance of PEP5

• The Bacillus subtilis endo-1,3-1,4-beta-glucanase gene (beg1) and the Butyrivibrio fibrisolvens endo-beta-1,4-glucanase gene (end1) were fused to the secretion signal sequence of the yeast mating pheromone alpha-factor (MF alpha 1S) and inserted between the yeast alcohol dehydrogenase II gene promoter (ADH2P) and terminator (ADH2T) [1].

High impact information on PEP5

• Two yeast mutants defective in the accumulation of an endocytotic marker, lucifer yellow CH, in the vacuole have been isolated. end1 accumulates invaginations of the plasma membrane, and end2, an internal membrane-bound organelle [2].
• The COOH-terminal 148 amino acids of Vps39 direct its association with the class C-Vps complex by binding to Vps11 [3].
• Moreover, the end1 mutant and all of the previously reported pep mutants, with the exception of pep4, were found to exhibit a profound vacuolar protein sorting defect, and complementation tests between the PEP, VPL VPT and END1 groups demonstrated that there are extensive overlaps between these groups [4].
• Characterization of the END1 gene required for vacuole biogenesis and gluconeogenic growth of budding yeast [5].
• DNA sequence analysis of the END1 gene reveals a 3090-bp open reading frame capable of encoding a hydrophilic protein of 118 kd [5].

Biological context of PEP5

• Together with the similar phenotypes exhibited by both vps11 and vps18 mutants, this finding suggests that they may function at a common step during vacuolar protein sorting and that the integrity of their zinc finger motifs may be required for this function [6].
• Pep3p and Pep5p are known to be necessary for trafficking of hydrolase precursors to the vacuole and for vacuolar biogenesis [7].
• Antibodies raised to a fusion protein that contained almost half of the PEP5 open reading frame allowed detection by immunoblot of a protein of relative molecular mass 107 kD in extracts prepared from wild-type cells [8].
• The PEP5 gene was isolated from a genomic DNA library by complementation of the pep5-8 mutation [8].
• Isolation and characterization of PEP5, a gene essential for vacuolar biogenesis in Saccharomyces cerevisiae [8].

Anatomical context of PEP5

• Our results suggest that a core Pep3p/Pep5p complex promotes vesicular docking/fusion reactions in conjunction with SNARE proteins at multiple steps in transport routes to the vacuole [7].
• PEP5 interacts genetically with VPS8, implicating Pep5p in the earlier Golgi to endosome step and/or in recycling from the endosome to the Golgi [7].
• This genetic interaction was unexpected, since Pep5p was thought to interact more directly with the vacuole, and Vps8p is thought to play a role in transport between the Golgi complex and the prevacuolar compartment [9].
• Two other genes, FHL1 and PEP5, are involved in the control of ribosome formation and vacuole biogenesis, respectively; and five genes, presently having unknown functions, could be new potentially interesting candidates for further studies in relation to yeast replicative aging [10].
• Since whole cell respiration and respiratory control of end1 mitochondria are not impaired, it seems plausible that a defect in gluconeogenesis could partially account for the inability of end1 to grow on non-fermentable carbon sources [5].

Associations of PEP5 with chemical compounds

• We identified a similar cysteine-rich motif near the COOH terminus of another Vps protein, the Vps11/Pep5/End1 protein [6].
• Yeast cells lacking a functional PEP3 or PEP5 gene are hypersensitive to copper and render the normally iron-repressible FET3 gene, encoding a multi-copper Fe(II) oxidase involved in Fe2+ transport, also repressible by exogenous copper ions [11].
• The predicted End1p sequence shows no significant similarity to other known protein sequences except for a short region of homology with the putative adenine nucleotide binding sites shared by a group of enzymes, notably ATPases [5].
• Enzyme assays confirmed that co-expression of EXG1, BEG1 and END1 enhanced glucan degradation by S. cerevisiae [1].

Physical interactions of PEP5

• Moreover, the Class D protein Vac1 was found to physically bind to the Class C Vps complex through a direct association with Vps11 [12].

Other interactions of PEP5

• The data are consistent with Pep5p functioning both at the site of Vps8p function and more closely proximal to the vacuole [9].
• These data suggest that Pep5p is a bifunctional protein and that the TRP1 insertion does not eliminate function, but results in a shorter peptide that can interact with Vps8-200p, allowing for partial function. vps8 deletion/disruption mutants contain a single enlarged vacuole [9].
• A more detailed investigation of pheromone response in the end1 mutant reveals that one aspect of the early response (induction of FUS1) is as defective as late responses (cell cycle arrest and projection formation) [13].
• These fingers also show limited conservation with S. cerevisiae VAC1, Vps11, and Vps18p proteins implicated in vacuolar transport [14].
• Secretion of End1p and Cel1p was directed by the signal sequence of the yeast mating pheromone alpha-factor (MF alpha 1), whereas Cbh1p and Bgl1p were secreted using their authentic leader peptides [15].

Analytical, diagnostic and therapeutic context of PEP5

• Cell fractionation showed the PEP5 gene product is enriched in the vacuolar fraction and appears to be a peripheral vacuolar membrane protein [8].
• The molecular mass of End1p was confirmed by immunoprecipitation [5].

References