FUNCTION OF N-TERMINAL IMPORT SIGNALS IN TRYPANOSOME MICROBODIES

The glycosomes of trypanosomes are related to eukaryotic peroxisomes. For many glycosomal and peroxisomal proteins, a C-terminal SKL-like tr ipeptide known as PTS-1 serves as the targeting signal. For peroxisome s, a second N-terminal signal (PTS-2) was demonstrated on rat 3-ketoac yl-CoA thiolase. Several glycosomal proteins do not bear a PTS-1. One such protein, fructose bisphosphate aldolase, has a PTS-2 homology at its N-terminus. To find out whether the PTS-2 pathway exists in trypan osomes, we expressed chloramphenicol acetyltransferase fusion proteins bearing N-terminal segments of either rat thiolase or trypanosome ald olase. The mammalian PTS-2 clearly mediated glycosomal import. The ald olase N-terminus mediated import with variable efficiency depending on the length of the appended sequence. These results provide evidence f or the existence of the PTS-2 pathway in trypanosomes.