Peroxisomal targeting of mammalian hydroxyacid oxidase 1 requires the C-terminal tripeptide SKI.
Peroxisomal proteins are post-translationally imported into peroxisomes after recognition by specific receptors. The best-defined peroxisomal targeting signal is a C-terminal tripeptide SKL. Different functional variants of this tripeptide have been defined, but mutants with a SKI sequence were recognized as being inefficiently targeted to peroxisomes. Recently, we have cloned a cDNA for the mouse hydroxyacid oxidase 1 (Hao1), a protein that seems to be localized in peroxisomes. Interestingly, the mouse Hao1 sequence comprises a C-terminal SKI tripeptide. We have analyzed the subcellular localization of Hao1 and tested whether its SKI sequence acts as a targeting signal. Ltk(-) and Cos-7 cells were transfected with vectors expressing a fusion protein of green fluorescence protein and Hao1, as well as mutants thereof. Targeting to peroxisomes of the fusion protein with the wild-type SKI sequence was highly selective and as complete as with the peroxisome-specific SKL sequence. By contrast, targeting was lost in a mutant with the sequence CKM. The data show that mammalian Hao1 is a peroxisomal protein and that the C-terminal sequence SKI acts as the targeting signal.
Recalcati
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Swiss Institute for Experimental Cancer Research, Ch. des Boveresses, CH-1066 Epalinges, s/Lausanne, Switzerland.
Menotti
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Kühn
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LC
D000429:Alcohol Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D017931:DNA Primers; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000378:metabolism*; D020675:Peroxisomes / Q000201:enzymology*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000201:enzymology
D017931:DNA Primers; D008164:Luminescent Proteins; D009842:Oligopeptides; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D000429:Alcohol Oxidoreductases; C020821:glycollate oxidase