Transport of Microinjected Proteins into the Peroxisomes of Mammalian Cells

Abstract

Peroxisomes are single-membrane-bound organelles found in virtually all eukaryotic cells. Proteins destined for the peroxisomes are synthesized on free polysomes in the cytoplasm and are transported into the peroxisome post-translationally (Fujiki et al., 1984). Although at least two proteins, thiolase and acyl-CoA oxidase, undergo proteolytic processing after transport (Fujiki et al., 1985), most proteins are synthesized at their mature size. Import of proteins into the peroxisome is dependent upon, among other factors, the presence of a peroxisomal targeting signal on the newly synthesized protein. A C-terminal tripeptide peroxisomal targeting signal (PUS) with the sequence serine-lysine-leucine-COOH (or a conservative variant) was identified initially in firefly luciferase (Gould et al., 1987), and has subsequently been found in most peroxisomal proteins (reviewed by Subramani, 1992).