Conservation of PEX19-binding motifs required for protein targeting to mammalian peroxisomal and trypanosome glycosomal membranes

Glycosomes are divergent peroxisomes found in trypanosomatid protozoa, including those that cause severe human diseases throughout much of the world. While peroxisomes are dispensable for both yeast (Saccharomyces cerevisiae and others) and mammalian cells in vitro, glycosomes are essential for trypanosomes and hence are viewed as a potential drug target. The import of proteins into the matrix of peroxisomes utilizes multiple peroxisomal membrane proteins which require the peroxin PEX19 for insertion into the peroxisomal membrane. In this report, we show that the specificity of peroxisomal membrane protein binding for Trypanosoma brucei PEX19 is very similar to those previously identified for human and yeast PEX19. Our studies show that trafficking is conserved across these distant phyla and that both a PEX19 binding site and a transmembrane domain are required for the insertion of two test proteins into the glycosomal membrane. However, in contrast to T. brucei PEX10 and PEX12, T. brucei PEX14 does not traffic to human peroxisomes, indicating that it is not recognized by the human PEX14 import mechanism.