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.
Halbach
André
A
Institut für Physiologische Chemie, Abt. Systembiochemie, Ruhr-Universität Bochum, 44780 Bochum, Germany.
Landgraf
Christiane
C
Lorenzen
Stephan
S
Rosenkranz
Katja
K
Volkmer-Engert
Rudolf
R
Erdmann
Ralf
R
Rottensteiner
Hanspeter
H
D001665:Binding Sites; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020675:Peroxisomes / Q000378:metabolism*; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*
D008565:Membrane Proteins; C110177:PEX15 protein, S cerevisiae; C474612:PEX26 protein, human; D010750:Phosphoproteins; D034741:RNA, Small Interfering; D029701:Saccharomyces cerevisiae Proteins; C087343:PEX19 protein, human