What type of targeting sequence do peroxisomal matrix proteins contain?
Peroxisomes single-membrane oxidative organelles ubiquitous eukaryotes performing fatty acid alpha beta-oxidation very long chain branched chain detoxifying hydrogen peroxide catalase plasmalogen ether lipid synthesis. Matrix content exceeding 50 enzymes imported post-translationally cytosol free ribosomes. Majority around 90 percent carry peroxisomal targeting signal type 1 PTS1 extreme C-terminus tripeptide (S/A/C)-(K/R/H)-(L/M) canonical most efficient Ser-Lys-Leu derived firefly luciferase discovery. Additional upstream residues modulate affinity receptor. PTS1 recognized tetratricopeptide TPR repeat domain soluble receptor Pex5 forming clamp binding tripeptide nanomolar affinity allowing folded oligomeric proteins cross translocon unique among organelles demonstrated import cross-linked 9 nm particles tetrameric catalase. PTS1 sufficient redirect heterologous non-peroxisomal reporters GFP to peroxisomes. Alternative signals: KDEL retains soluble proteins ER via COPI retrieval, NPXY internalization drives clathrin-mediated endocytosis via PTB adaptors Dab2 ARH linking AP2, DXE directs ER exit COPII vesicles Sec24 binding. Mutation deletion SKL abolishes import causing cytosolic mislocalization as Zellweger spectrum disorders with very long chain fatty acid accumulation clinical severity and developmental defects.
Ref: Lodish et al., MCB: PTS1 SKL tripeptide targets matrix proteins to peroxisomes.