title: Processing of the glycosomal matrix-protein import receptor PEX5 of Trypanosoma brucei.
abstract: Glycolysis in kinetoplastid protists such as Trypanosoma brucei is compartmentalized in peroxisome-like organelles called glycosomes. Glycosomal matrix-protein import involves a cytosolic receptor, PEX5, which recognizes the peroxisomal-targeting signal type 1 (PTS1) present at the C-terminus of the majority of matrix proteins. PEX5 appears generally susceptible to in vitro proteolytic processing. On western blots of T. brucei, two PEX5 forms are detected with apparent M(r) of 100kDa and 72kDa. 5'-RACE-PCR showed that TbPEX5 is encoded by a unique transcript that can be translated into a protein of maximally 72kDa. However, recombinant PEX5 migrates aberrantly in SDS-PAGE with an apparent M(r) of 100kDa, similarly as observed for the native peroxin. In vitro protease susceptibility analysis of native and (35)S-labelled PEX5 showed truncation of the 100kDa form at the N-terminal side by unknown parasite proteases, giving rise to the 72kDa form which remains functional for PTS1 binding. The relevance of these observations is discussed.
authors.affiliation: Research Unit for Tropical Diseases, de Duve Institute, Université catholique de Louvain, Brussels, Belgium.
authors.forename: Melisa
authors.initials: M
authors.lastname: Gualdrón-López
authors.forename: Paul A M
authors.initials: PA
authors.lastname: Michels
mesh_terms: D010447:Peptide Hydrolases / Q000737:chemistry; D000074435:Peroxisome-Targeting Signal 1 Receptor; D017434:Protein Structure, Tertiary; D059748:Proteolysis; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry* / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D014346:Trypanosoma brucei brucei / Q000235:genetics / Q000378:metabolism*
chemical_list: D000074435:Peroxisome-Targeting Signal 1 Receptor; D015800:Protozoan Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D011994:Recombinant Proteins; D010447:Peptide Hydrolases