TARGETING PROTEINS TO THE GLYCOSOMES OF AFRICAN TRYPANOSOMES

Authors
Citation
Jm. Sommer et Cc. Wang, TARGETING PROTEINS TO THE GLYCOSOMES OF AFRICAN TRYPANOSOMES, Annual review of microbiology, 48, 1994, pp. 105-138
Citations number
217
Categorie Soggetti
Microbiology
ISSN journal
00664227
Volume
48
Year of publication
1994
Pages
105 - 138
Database
ISI
SICI code
0066-4227(1994)48:<105:TPTTGO>2.0.ZU;2-U
Abstract
Glycosomes are microbodies found in protozoa belonging to the order Ki netoplastida. These highly specialized organelles compartmentalize mos t of the glycolytic enzymes normally located in the cytosol of other e ukaryotic cells. The recent success in expressing foreign proteins in Trypanosoma brucei has permitted a detailed analysis of glycosomal pro tein targeting signals in these organisms. These studies have revealed that the previously identified C-terminal tripeptide peroxisomal targ eting signal also functions in the import of proteins into the glycoso mes of T. brucei. However, the glycosomal and peroxisomal targeting si gnals differ in a few important ways. The C-terminal tripeptide sequen ce requirements for glycosomal protein targeting are comparatively rel axed. Of the three C-terminal amino acids, the first can be any small, neutral amino acid; the second should be capable of forming hydrogen bondings, whereas the third is a hydrophobic amino acid. This degenera te tripeptide sequence differs significantly from the more stringent r equirements observed for the import of proteins into mammalian peroxis omes and thus represents an opportunity for designing peptide analogue s that specifically block the glycosomal protein import for a possible antitrypanosomal chemotherapy. A recently described N-terminal signal that targets thiolase to the mammalian peroxisomes does not appear to function in import into the glycosomes. However, a novel internal tar geting signal has tentatively been identified in at least one of the g lycosomal proteins that can target a reporter protein to the glycosome s of T. brucei. Glycosome-deficient mutants have been isolated recentl y, which will aid in the identification of genes involved in the bioge nesis of the glycosome.