Identification of PEX33, a novel component of the peroxisomal docking complex in the filamentous fungus Neurospora crassa

The docking complex of peroxisomal matrix protein import is composed of PEX13 and PEX14 in all species analyzed so far, whereas only yeast appears to possess an additional component, PEX17. In this report we isolated PEX14 complexes of Neurospora crassa. Among the complex constituents, one protein designated as PEX33 possessed homology to PEX14 but only in a short N-terminal domain. The PEX14/PEX33 interaction was verified by means of two-hybrid analysis. Moreover, PEX33 was shown to interact with itself and the PTS1-receptor PEX5. Localization studies demonstrated that PEX33 constitutes a glyoxysomal protein. Growth tests of the pex33 deletion strain revealed a defect of this strain in the biogenesis of glyoxysomes and Woronin bodies. As the function of PEX33 was not redundant to that of PEX14, it is a genuine novel peroxin. Based on our experimental data, the function of PEX33 seems to resemble that of yeast PEX17 despite clear structural differences.