Targeting of the tail-anchored peroxisomal membrane proteins PEX26 and PEX15 occurs through C-terminal PEX19-binding sites.
Tail-anchored proteins contain a single transmembrane domain (TMD) followed by a short C-terminal domain extending into the organellar lumen. Tail-anchored proteins are thought to target to the correct subcellular compartment by virtue of general physicochemical properties of their C-termini; however, the machineries that enable correct sorting remain largely elusive. Here we analyzed targeting of the human peroxisomal tail-anchored protein PEX26. Its C-terminal-targeting signal contains two binding sites for PEX19, the import receptor for several peroxisomal membrane proteins. One PEX19-binding site overlapped with the TMD, the other was contained within the luminal domain. Although the PEX19-binding site containing the TMD targeted to peroxisomes to some extent, the luminal site proved essential for correct targeting of the full-length protein, as it prevented PEX26 from mislocalization to mitochondria. Its function as a targeting motif was proved by its ability to insert a heterologous TMD-containing fragment into the peroxisomal membrane. Finally we show that PEX19 is essential for PEX26 import. Analysis of the yeast tail-anchored protein Pex15p revealed that it also harbors a luminal PEX19-binding site that acts as a peroxisomal-targeting motif. We conclude that C-terminal PEX19-binding sites mark tail-anchored proteins for delivery to peroxisomes.[1]References
- Targeting of the tail-anchored peroxisomal membrane proteins PEX26 and PEX15 occurs through C-terminal PEX19-binding sites. Halbach, A., Landgraf, C., Lorenzen, S., Rosenkranz, K., Volkmer-Engert, R., Erdmann, R., Rottensteiner, H. J. Cell. Sci. (2006) [Pubmed]
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