To investigate the synthesis of alpha2-fucosylated epitopes in the bovine species, we have characterized cDNAs from various tissues. We found three distinct alpha2-fucosyltransferase genes, named bovine fut1, fut2, and sec1 which are homologous to human FUT1, FUT2, and Sec1 genes, respectively. Their open reading frames (ORF) encode polypeptides of 360 (bovine H), 344 (bovine Se), and 368 (bovine Sec1) amino acids, respectively. These enzymes transfer fucose in alpha1,2 linkage to ganglioside GM(1)and galacto- N -biose, but not to the phenyl-beta-D-galactoside, type 1 or type 2 acceptors, suggesting that their substrate specificity is different and more restricted than the other cloned mammalian alpha2-fucosyltransferases. Southern blot analyses detected four related alpha2-fucosyltransferase sequences in the bovine genome while only three have been described in other species. The supernumerary entity seems to be related to the alpha2-fucosyltransferase activity which can also use type 1 and phenyl-beta-D-galactoside substrate acceptors. It was exclusively found in bovine intestinal tract. Our results show that, at least in one mammalian species, four alpha2-fucosyltransferases are present, three adding a fucose on alpha1,2 linkage on type 3/4 acceptor (Galbeta1-3GalNAc) and another able to transfer also fucose on phenyl-beta-D-galactoside and type 1 (Galbeta1-3GlcNAc) acceptors. The phylogenetic tree of the enzymes homologous to those encoded by the bovine fut1, fut2, and sec1 genes revealed two main families, one containing all the H-like proteins and the second containing all the Se-like and Sec1-like proteins. The Sec1-like family had a higher evolutionary rate than the Se-like family.

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By referring to the split coding sequence of the highly conserved alpha 6-fucosyltransferase gene family (assumed to be representative of the common alpha 2 and alpha 6 fucosyltransferase gene ancestor), we have hypothesized that the monoexonic coding sequences of the present alpha 2-fucosyltransferase genes have been shaped in mammals by several events of retrotransposition and/or duplication. In order to test our hypothesis, we determined the structure of the three bovine alpha 2-fucosyltransferase genes (bfut1, bfut2, and sec1) and analyzed their characteristics compared with their human counterparts (FUT1, FUT2, and Sec1). We show that in mammals, a complex nonautonomous L1-retrotransposition event occurred within the locus of the alpha 2-fucosyltransferase ancestor gene itself. A consequence of this event was the processing in Catarrhini of a Sec1 pseudogene via several point mutations.

. 176:6170-6174, 1994), an ENGase activity having the same substrate specificity was also found to be secreted during vegetative growth of Myxococcus xanthus DK1622. The activity decreased in mutants known to secrete less protein than the wild type (Exc ؎ ). During submerged development, the activity was produced in two steps: the first increase occurred during the aggregation phase, and the second one occurred much later, during spore formation. This production was lower in developmental mutants impairing cell-cell signaling, the late mutants (csg and dsg) being the most deficient. Finally, when sporulation was obtained either by starvation in liquid shake flask culture or by glycerol induction, the activity was produced exclusively by the wild-type cells during the maturation of the coat.Myxococcus xanthus is a gram-negative soil bacterium characterized by its complex life cycle in which developmental stages in addition to vegetative growth are observed. When starved on a solid-liquid interface, M. xanthus is able to undergo a development cycle yielding multicellular fruiting bodies in which 20% of the ca. 10 5 constituent cells have differentiated into dormant myxospores. To perform this multicellular morphogenesis, M. xanthus produces cell-cell signaling molecules, as shown by nonautonomous developmental mutants that cannot develop in their absence (the A, B, C, D, and more recently found E factors). These mutants arrest development at different stages, with those preventing production of A and B factors (belonging to asg and bsg loci, respectively) being arrested prior to the aggregation phase only 2 to 3 h into the developmental program (15).M. xanthus secretes numerous extracellular proteins during vegetative growth that enable the cells to lyse and hydrolyze their prey. Mutants belonging to five unlinked loci produce most of these proteins at a reduced rate. Among them, three (asgA, asgB, and asgC) are impaired in A-factor production, described formerly, and the other two (excA and excB) are also unable to undergo normal development (10).Although it is known that numerous extracellular proteins are produced during vegetative growth, few have been characterized or purified so far, and these are mainly lytic enzymes such as cell wall lytic enzymes (35) and proteases (4,6,9,21,29). Recently, it has been established (31) that some secreted trypsin-like proteases from M. xanthus were a component of the above-mentioned A factor, a complex mixture of amino acids, peptides, and proteases which induces the differentiation pathway of this bacterium after starvation.We have recently demonstrated that another myxobacterium, Stigmatella aurantiaca DW4, secretes during vegetative growth an endo-N-acetyl-␤-D-glucosaminidase (ENGase), named ENGase St, acting on the di-N-acetylchitobiosyl part of N-linked glycans (2). ENGase St was the first such enzyme to be detected in myxobacteria. ENGases were found to be secreted by many bacteria (22), but their possible function in the cells was not investigated.To suggest a role o...

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