Molecular Requirements for Peroxisomal Targeting of Alanine-Glyoxylate Aminotransferase as an Essential Determinant in Primary Hyperoxaluria Type 1

Abstract

The crystal structure of the peroxisome enzyme alanine-glyoxylate aminotransferase bound to its targeting receptor Pex5p explains why even minor fold defects prevent targeting of the enzyme and cause kidney disease.

Structural Insights into Cargo Recognition by the Yeast PTS1 Receptor

“…6) based on the known three-dimensional structures of human and trypanosome Pex5p (17,50). Besides protein and species-dependent amino acid variations of the PTS1 (9), the structure of the signal sequence seems to be very similar, as shown for SCP2 (sterol carrier protein 2), and the YQSKL peptide (16,17,59,60). Sites of interaction of human PEX5 with the PTS1 of SCP2 and AGT revealed five conserved asparagines at the ␣-helices of TPR3, TPR6, and TPR7 of Pex5p (21,59).…”

“…However, for none of these yeast proteins, the receptor interface has been defined in structural terms. Crystal structures of human PEX5-cargo complexes also revealed secondary binding sites, which were shown to increase the binding affinity to PEX5 (19,59,62). Although the interacting region of the cargo SCP2 is far apart from the PTS1-binding site, the second PEX5-binding site of AGT is next to its C terminus and thereby resembles that of Pcs60p.…”

“…Nevertheless, substitution of the five amino acids adjacent to the SKL also abolished import, underlining that the importance of this low affinity binding region is essential for the functionality of the targeting signal. For other cargo proteins, K D values in the micromolar range are sufficient for peroxisomal import (59). Thus, alternatively, the presence of the PTS1 might trigger conformational changes in Pex5p that render it competent for subsequent import.…”

“…10). It has been suggested that additional binding regions of AGT promote the non-autonomous binding of the non-canonical targeting sequence KKL (59,62). However, Pcs60p carries the strong targeting signal SKL, which binds with high affinity to the yeast Pex5p receptor site but still requires the adjacent region for peroxisomal targeting.…”

Novel insights into renal d-amino acid oxidase accumulation: propiverine changes DAAO localization and peroxisomal size in vivo

“…Generally, peroxisomes are known to be highly variable in size, shape, number and protein content (Fransen 2012); nevertheless, to the best of our knowledge, a significant decrease in peroxisomal size after drug administration was not reported so far for mammalian cells. Interestingly, it is reported that peroxisomal proteins can be differentially localized within the cell depending on differential splicing, multiple targeting signals or phosphorylation (Fordor et al 2012;Ast et al 2013). However, dual localization of peroxisomal proteins was predominantly reported to occur into the cytosol and into mitochondria (Ast et al 2013), merely one study in yeast described nuclear translocation of a peroxisomal NAD + -dependent glycerol 3-phosphate dehydrogenase (Jung et al 2010).…”