A conserved alpha helical domain at the N-terminus of Pex14p is required for PTS1 and PTS2 protein import in Hansenula polymorpha

We have analyzed the highly conserved N-terminus of Hansenula polymorpha Pex14p for its function in peroxisomal matrix protein import. The region comprising aa 10–54 of HpPex14p is predicted to contain three α-helices. Its α-helical structure was confirmed by CD analysis of a synthetic peptide, corresponding to residues 8–58. Deletion of aa 1–21 of HpPex14p, but not of aa 1–9, completely abolished PTS1 and PTS2 matrix protein import. An extensive mutational analysis of the first α-helix (aa 10–21) demonstrated that its secondary structure, as well as residues Phe20 and Leu21, are essential for PTS1 and PTS2 matrix protein import.