The cytoplasmic and transmembrane domains of secretor type alpha1,2fucosyltransferase confer atypical cellular localisation.

Abstract

Carbohydrate structures influence many aspects of cell biology. Manipulating the glycosyltransferase enzymes, that sequentially add carbohydrate moieties to proteins and lipids as they pass through the Golgi and secretory pathway, can alter these carbohydrate epitopes. We previously demonstrated that the eight amino acid cytoplasmic tail of alpha1,2fucosyltransferase (FT) contained a sequence for Golgi localisation. In this study, we examined the localisation of the closely related secretor type alpha1,2fucosyltransferase (Sec) which has a smaller, yet apparently unrelated, five amino acid cytoplasmic tail. In contrast to the Golgi localisation of FT, Sec displayed atypical cytoplasmic vesicular-like staining. However, replacing just the five amino acid tail of Sec with FT was sufficient to relocalise the enzyme to a perinuclear region with Golgi-like staining. The biological significance of this relocalisation was this chimaeric enzyme was more effective than FT at competing for N-Acetyl-lactosamine and thus was superior in reducing expression of the Galalpha(1,3)Gal xenoepitope.