All eukaryotes so far studied, including animals, plants, yeasts and trypanosomes, have two pathways to target proteins to peroxisomes. These two pathways are specific for the two types of peroxisome targeting signal (PTS) present on peroxisomal matrix proteins. Remarkably, the complete genome sequence of Caenorhabditis elegans lacks the genes encoding proteins specific for the PTS2 targeting p...

The determination of the NMR structure of the sterol carrier protein-2 (SCP2), analysis of backbone (15)N spin relaxation parameters and NMR studies of nitroxide spin-labeled substrate binding are presented as a new basis for investigations of the mode of action of SCP2. The SCP2 fold is formed by a five-stranded beta-sheet and four alpha-helices. Fatty acid binding to a hydrophobic surface are...

Pex14p, an S. cerevisiae peroxin, is attached to the outer face of the peroxisomal membrane and is a component of the protein import machinery. Pex14p interacts with both the PTS1 and PTS2 receptors. It is the only known peroxisomal membrane protein that binds the PTS2 receptor and might thus mediate the membrane docking event of PTS2-dependent protein import. These results suggest that the two...

Protein import into the peroxisome matrix is mediated by peroxisome-targeting signals (PTSs). We have developed a novel, quantitative, in vitro assay for measuring peroxisomal import of PTS1-containing proteins. This enzyme-linked immunosorbent assay-based system utilizes semi-intact human A431 cells or fibroblasts and a biotinylated version of the PTS1-containing import substrate, luciferase. ...

We have isolated the Saccharomyces cerevisiae pex12-1 mutant from a screen to identify mutants defective in peroxisome biogenesis. The pex12delta deletion strain fails to import peroxisomal matrix proteins through both the PTS1 and PTS2 pathway. The PEX12 gene was cloned by functional complementation of the pex12-1 mutant strain and encodes a polypeptide of 399 amino acids. ScPex12p is ortholog...

Peroxisomal matrix protein import uses two peroxisomal targeting signals (PTSs). Most matrix proteins use the PTS1 pathway and its cargo receptor, Pex5. The PTS2 pathway is dependent on another receptor, Pex7, and its coreceptor, Pex20. We found that during the matrix protein import cycle, the stability and dynamics of Pex7 differ from those of Pex5 and Pex20. In Pichia pastoris, unlike Pex5 an...

The distribution of alanine:glyoxylate aminotransferase 1 (AGT) within liver cells has changed many times during mammalian evolution. Depending on the particular species, AGT can be found in mitochondria or peroxisomes, or mitochondria and peroxisomes. In some cases significant cytosolic AGT is also present. In the livers of most rodents, AGT has what is thought to be the more 'ancestral' distr...

Within the extended receptor cycle of peroxisomal matrix import, the function of the import receptor Pex5p comprises cargo recognition and transport. While the C-terminal half (Pex5p-C) is responsible for PTS1 binding, the contribution of the N-terminal half of Pex5p (Pex5p-N) to the receptor cycle has been less clear. Here we demonstrate, using different techniques, that in Saccharomyces cerev...

To elucidate unknown mammalian peroxisomal enzymes and functions, we subjected M13 phage expressing fusions between the gene encoding protein VI and a rat liver cDNA library to an immunoaffinity selection process in vitro (biopanning) with the use of antibodies raised against peroxisomal subfractions. In an initial series of biopanning experiments, four different cDNA clones were obtained. Thes...