The peroxisomal membrane protein Pex14p of Hansenula polymorpha is phosphorylated in vivo.

Hansenula polymorpha Pex14p (HpPex14p) is a component of the peroxisomal membrane essential for peroxisome biogenesis. Here, we show that HpPex14p is phosphorylated in vivo. In wild-type H. polymorpha cells, grown in the presence of [32P]orthophosphate, the 32P label was incorporated into HpPex14p. Labelled HpPex14p was induced after a shift of cells to methanol-containing media and rapidly disappeared after a shift to glucose medium, which induces specific peroxisome degradation. Alkaline phosphatase treatment of labelled HpPex14p resulted in the release of 32P and a minor shift of the HpPex14p band on Western blots. Phosphoamino acid analysis by two dimensional silica gel thin layer chromatography suggested that the major phosphoamino acid in phosphorylated HpPex14p was acid-labile.