Investigating targeting of the 22 kDa peroxisomal membrane protein (Pmp22p) to the peroxisomal membrane we have confined the targeting signal to amino acid residues 16–37 located in the N-terminal cytoplasmic tail. Comparison of Pmp22p orthologous sequences revealed a conserved motif Y3xL3xP3x(KQN) which might represent the core of this targeting signal not found so far in other Pmps. Fusion of the Pmp22p N-terminal tail to the C-terminal portion of Pmp22p which per se is not targeted to peroxisomes, conveys peroxisomal targeting. These data suggest that Pmp22p is targeted to peroxisomes by a new membrane targeting signal which is necessary and sufficient to target a polypeptide containing two transmembrane spans to peroxisomes.
