ABSTRACT
The biosynthesis of guanosine 5′-diphospho-β-L-fucose (GDP-Fuc), the activated donor for fucose, has been shown to be essential in the parasite Trypanosoma brucei. Fucose is a common constituent of eukaryotic glycan structures, but it has been rarely found in trypanosomatid glycoconjugates. A single putative T. brucei fucosyltransferase (TbFUT1) gene was identified in the trypanosome genome. The encoded TbFUT1 protein was enzymatically active when expressed in Escherichia coli. Structural characterization of its reaction products identified it as a GDP-Fuc: β-D-galactose α-1,2-fucosyltransferase, with a preference for a Galβ1,3GlcNAcβ1-O-R acceptor motif among the substrates tested. Conditional null mutants of the TbFUT1 gene demonstrated that it is essential for growth of the mammalian-infective bloodstream form and insect vector dwelling procyclic form of the parasite. Unexpectedly, TbFUT1 was localized in the mitochondrion of T. brucei and found to be essential for mitochondrial function in bloodstream form trypanosomes, suggesting this kinetoplastid parasite possesses an unprecedented and essential mitochondrial fucosyltransferase activity.
SIGNIFICANCE The sugar fucose is a well-known component of cell-surface glycoproteins and glycolipids and typically plays roles in cell-cell adhesion. Fucose is generally incorporated into glycoproteins and glycolipids by fucosyltransferase enzymes that reside in the Golgi apparatus. Here we show that the single fucosyltransferase of the protozoan parasite Trypanosoma brucei, causative agent of human and animal African trypanosomiasis, resides in the mitochondrion and not the Golgi apparatus. While the exact role of fucosylation in the parasite mitochondrion remains to be determined, it is essential for mitochondrial function and for parasite growth and survival. The unusual nature of this parasite enzyme, and its orthologues in related parasite pathogens, suggests that selective inhibitors may have therapeutic potential across a family of parasites.