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Investigating the regulation of peroxisome biogenesis

Peroxins (PEXs) or peroxisome biogenesis factors include proteins responsible for the import of folded peroxisomal matrix proteins. PEX5, which recognizes and binds PTS1 cargo motifs, and the docking machinery (PEX13 and PEX14) on the peroxisomal membrane are phosphorylated (Kataya et al., 2019). Interestingly, two phosphorylated serine residues (S308, S328) are located within a series of nine WXXXF/Y repeats in PEX5, which are responsible for binding with PEX14 (Kataya et al., 2019). Indeed, the missense allele showing a single mutation of S318 to Leu in the mutant PEX5-1 impacted the sucrose dependence phenotype and affected PTS2-mediated import. PEX14 also has constitutive phosphorylation that was also detected in our proteome studies. Using the WT protein and versions with mutated phosphorylated-residues, we have complemented the mutant pex14 , pex5-1 and pex5-10, which also show a sugar-dependent phenotype. Results will potentially indicate the importance of phosphorylation on regulating peroxisome protein import.