FIG. 1.

Import of peroxisomal proteins. (A, B) Peroxisomal matrix proteins synthesized on cytoplasmic ribosomes (R) possess one of two distinct amino acid sequences called peroxisomal targeting signal (PTS) 1 and PTS2. Peroxisomal targeting signals are recognized and bound by specific cytosolic receptors, PTS1 by peroxin (PEX) 5 and PTS2 by PEX7. (C) The protein–receptor complexes are transported to peroxisomes (P) where they interact with PEX14 and dock to the peroxisomal membrane. (D) Next, the protein–receptor complexes are translocated across the membrane and the proteins are released into the peroxisome matrix. (E) After the release of cargo proteins, PEX5 and PEX7 shuttle back to the cytosol. Peroxisomal membrane proteins have a membrane peroxisomal targeting signal (mPTS) that is recognized by PEX19. PEX19 transports the membrane proteins to peroxisomes where they dock to PEX3. Subsequently, the proteins are integrated into the peroxisome membrane and PEX19 is released back to the cytosol. To see this illustration in color, the reader is referred to the web version of this article at www.liebertpub.com/ars