Conserved structural features in eukaryotic and prokaryotic fucosyltransferases

Abstract

Fucosyltransferases are the enzymes transferring fucose from GDP-Fuc to Gal in an α1,2-linkage and to GlcNAc in α1,3-, α1,4- or α1,6-linkages. Since all fucosyltransferases utilize the same nucleotide sugar, their specificity will probably reside in the recognition of the acceptor and in the type of linkage formed. A search of nucleotide and protein databases yielded more than 30 sequences of fucosyltransferases originating from mammals, chicken, nematode, and bacteria. On the basis of protein sequence similarities, these enzymes can he classified into four distinct families: (1) the α-2-fucosyltransferases, (2) the α-3-fucosyltransferases, (3) the mammalian α-6-fucosyltransferases, and (4-) the bacterial α-6-fucosyltransferases. Nevertheless, using the sensitive hydrophobic cluster analysis (HCA) method, conserved structural features as well as a consensus peptide motif have been clearly identified in the catalytic domains of all α-2 and α-6-fucosyltranferases, from prokaryotic and eukaryotic origin, that allowed the grouping of these enzymes into one superfamily. In addition, a few amino acids were found strictly conserved in this family, and two of these residues have been reported to be essential for enzyme activity for a human α-2-fucosyltransferase. The α-3-fucosyltransferases constitute a distinct family as they lack the consensus peptide, but some regions display similarities with the α-2 and α-6-fucosyltranferases. All these observations strongly suggest that the fucosyltransferases share some common structural and catalytic features.