Peroxisomal-matrix targeting sequences

NLS, nuclear localization signal PTS, peroxisomal-matrix targeting sequence. 

Cytosolic Receptor Targets Proteins with an SKL Sequence at the C-Terminus into the Peroxisomal Matrix... 

The import of catalase and other proteins into rat liver peroxisomes can be assayed in a cell-free system similar to that used for monitoring mitochondrial protein Import (see Figure 16-25). By testing various mutant catalase proteins in this system, researchers discovered that the sequence Ser-Lys-Leu (SKL in one-letter code) or a related sequence at the C-terminus was necessary for peroxisomal targeting. Further, addition of the SKL sequence to the C-termlnus of a normally cytosolic protein leads to uptake of the altered protein by peroxisomes in cultured cells. All but a few of the many different peroxisomal matrix proteins bear a sequence of this type, known as peroxisomal-targeting sequence 1, or simply PTSl. 

Most peroxisomal matrix proteins contain a C-termlnal PTSl targeting sequence a few have an N-termlnal PTS2 targeting sequence. Neither targeting sequence is cleaved after Import. 

Proteins destined for the peroxisomal membrane contain different targeting sequences than peroxisomal matrix proteins and are imported by a different pathway. 

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