High impact information on PEX13

• Pex14p also interacts with two other membrane-bound peroxins including Pex13p, another binding protein for the PTS1 receptor [1].
• Recently, many SH3 domains, including those from Grb2 and Pex13p, were reported to bind sequences lacking a PxxP motif [2].
• The binding site of the Grb2 SH3 partially overlapped the conventional PxxP-binding site, whereas those of p67(phox) and Pex13p SH3s are located in different surface regions [2].
• Pex13p is the putative docking protein for peroxisomal targeting signal 1 (PTS1)-dependent protein import into peroxisomes [3].
• Reinvestigation of the topology revealed both termini of Pex13p to be oriented towards the cytosol [3].

Biological context of PEX13

• Proteins homologous to PEX12 and PEX13 have previously been found in Arabidopsis but it is not known whether they are involved in protein transport to peroxisomes [4].
• Saccharomyces cerevisiae PTS1 receptor Pex5p interacts with the SH3 domain of the peroxisomal membrane protein Pex13p in an unconventional, non-PXXP-related manner [5].
• Furthermore, these cells are homozygous for a missense mutation at a conserved position in the PEX13 SH3 domain [6].
• A point mutation in the COOH-terminal Src homology 3 (SH3) domain of Pex13p inactivated the protein but did not affect its membrane targeting [7].

Anatomical context of PEX13

• Pex13p deficient cells retain membranes containing the peroxisomal membrane protein Pex11p (former Pmp27p), consistent with the existence of independent pathways for the integration of peroxisomal membrane proteins and for the translocation of peroxisomal matrix proteins [8].
• Subsequently, the formed Pex7p/cargo complex is transported from the cytosol to the peroxisomal docking complex, consisting of Pex13p and Pex14p [9].
• A peroxisomally targeted Pex13p fragment became mislocalized to the endoplasmic reticulum in the absence of its Pex19p-binding site [10].

Physical interactions of PEX13

• This conclusion is supported by immunoprecipitation experiments showing that Pex14p and Pex17p coprecipitate with both PTS receptors in the absence of Pex13p [11].
• In the yeast Saccharomyces cerevisiae, both Pex5p and Pex14p are able to bind Pex13p via its SH3 domain [5].

Other interactions of PEX13

• Here we mapped the Pex7p interaction domain of Pex13p to its N-terminal 100 amino acids [9].
• The pas (peroxisome assembly) mutants that have been used for complementation analysis represent 12 complementation groups including three novel ones, designated pas20, pas21 and pas22 [12].

References