Divergent evolution of fucosyltransferase genes from vertebrates, invertebrates, and bacteria

Abstract

On the basis of function and sequence similarities, the vertebrate fucosyltransferases can be classified into three groups: α-2-, α-3-, and α-6-fucosyltransferases. Thirty new putative fucosyltransferase genes from invertebrates and bacteria and six conserved peptide motifs have been identified in DNA and protein databanks. Two of these motifs are specific of α-3fucosyltransferases, one is specific of α-2-fucosyltransferases, another is specific of α-6-fucosyltransferases, and two are shared by both α-2- and α-6-fucosyltranserases. Based on these data, literature data, and the phylogenetic analysis of the conserved peptide motifs, a model for the evolution of fucosyltransferase genes by successive duplications, followed by divergent evolution is proposed, with either two different ancestors, one for the α-2/6-fucosyltransferases and one for the α-3-fucosyltransferases or a single common ancestor for the two families. The expected properties of such an hypothetical ancestor suggest that the plant or insect α-3-fucosyltransferases using chitobiose as acceptor might be the present forms of this ancestor, since fucosyltransferases using chitobiose as acceptor are expected to be of earlier appearance in evolution than enzymes using N-acetyllactosamine. However, an example of convergent evolution of fucosyltransferase genes is suggested for the appearance of the Le^a epitopes found in plants and primates.