title: Predominant localization of non-specific lipid-transfer protein of the yeast Candida tropicalis in the matrix of peroxisomes.
abstract: PXP-18 is a 14-kDa major peroxisomal protein of the yeast Candida tropicalis and a homologue of the non-specific lipid-transfer protein (nsLTP) of mammals. Mammalian nsLTP is thought to facilitate the contact of membranes, to stimulate lipid-transfer between them. If PXP-18 functions like nsLTP, it must be present on organelle membranes. Immunoelectron microscopy of C. tropicalis cells indicated that gold particles, which visualized PXP-18, localized exclusively in the matrix of peroxisomes. Subcellular fractionation followed by Western blotting revealed the association of PXP-18 with peroxisomes in C. tropicalis cells. An enzyme-linked immunosorbent assay revealed that almost all the PXP-18 associated with peroxisomes was detectable after the solubilization of the organelle but not before, implying the predominance of PXP-18 inside peroxisomes. This differential assay was applied to the intracellular import of the intact and truncated PXP-18s expressed in Saccharomyces cerevisiae cells. Most of the intact PXP-18 was shown to be imported into the matrix of host-cell peroxisomes, whereas the truncated PXP-18, which lacked the C-terminal tripeptide Pro-Lys-Leu, no longer targeted peroxisomes. These results are consistent with the view that PXP-18 is the matrix protein of peroxisomes and must function in a system other than that of lipid transfer.
authors.affiliation: Faculty of Integrated Arts and Sciences, Hiroshima University, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Tan
authors.forename: M
authors.initials: M
authors.lastname: Bun-Ya
authors.forename: A
authors.initials: A
authors.lastname: Hirata
authors.forename: T
authors.initials: T
authors.lastname: Kamiryo
mesh_terms: D000595:Amino Acid Sequence; D000908:Antibodies, Fungal; D000918:Antibody Specificity; D001692:Biological Transport; D002175:Candida / Q000737:chemistry* / Q000648:ultrastructure; D002451:Cell Compartmentation; D002458:Cell Fractionation; D004797:Enzyme-Linked Immunosorbent Assay; D005656:Fungal Proteins / Q000276:immunology / Q000302:isolation & purification*; D050356:Lipid Metabolism; D008830:Microbodies / Q000737:chemistry*; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D014170:Transformation, Genetic
chemical_list: D000908:Antibodies, Fungal; D005656:Fungal Proteins; D011994:Recombinant Proteins; C090867:POX18 protein, Candida tropicalis