Characterization of a Binary Tandem Domain F-type Lectin from Striped Bass (Morone saxatilis)

Abstract

Among other functions, lectins play an important role in the innate immune response of vertebrates and invertebrates by recognizing exposed glycans on the surface of potential pathogens. Despite the typically weak interaction of lectin domains with their carbohydrate ligands, they usually achieve high avidity through oligomeric structures or by the presence of tandem carbohydratebinding domains along the polypeptide. The recently described structure of the fucose-binding European eel agglutinin revealed a novel lectin fold (the "F-type" fold), which is shared with other carbohydrate-binding proteins and apparently unrelated proteins from prokaryotes to vertebrates, and a unique fucose-binding sequence motif. Here we described the biochemical and molecular characterization of a unique fucose-binding lectin (MsaFBP32) isolated from serum of the striped bass (Morone saxatilis), composed of two tandem domains that exhibit the eel carbohydrate recognition sequence motif, which we designate F-type. We also described a novel lectin family ("F-type") constituted by a large number of proteins exhibiting greater multiples of the F-type motif, either tandemly arrayed or in mosaic combinations with other domains, including a putative transmembrane receptor, that suggests an extensive functional diversification of this lectin family. Among the tandem lectins, MsaFBP32 and other tandem binary homologues appear unique in that although their N-terminal domain shows close similarity to the fucose recognition domain of the eel agglutinin, their C-terminal domain exhibits changes that potentially could confer a distinct specificity for fucosylated ligands. In contrast with the amniotes, in which the F-type lectins appear conspicuously absent, the widespread gene duplication in the teleost fish suggests these F-type lectins acquired increasing evolutionary value within this taxon.

Isolation and characterization of a fish F-type lectin from gilt head bream (Sparus aurata) serum

“…Recently, a novel family of fucose-binding lectins was identified by Odom and Vasta [15]. These lectins possess characteristic L-fucose-binding and calcium-binding sequence motifs, and a unique lectin fold [18].…”

“…These lectins possess characteristic L-fucose-binding and calcium-binding sequence motifs, and a unique lectin fold [18]. The F-lectin sequence motif has a wide phylogenetic distribution being found in eubacteria, molluscs, arthropods, echinoderms, fish, and amphibians, but appears to be absent from protozoa, fungi, nematodes, ascidians and amniotes such as birds and mammals [15]. In some species, the F-type carbohydrate-binding domain may be associated with other structural domains including pentraxin, other lectin domains such as, C-type lectin, or complement control "sushi" domains to yield complex chimaeric proteins, such as the Drosophila melanogaster furrowed and the CG9095 protein [15].…”

“…Isolation of total RNA from liver, synthesis of first strand cDNA and cDNA cloning Total RNAs from Dicentrarchus labrax and Sparus aurata were isolated from liver by using a RNAqueousTM-Midi Kit purification system (Ambion) and reverse transcribed with a Ready-to-Go T-primed first-strand using random primers (Amersham Biosciences). Amplification was performed using 1 mM of the degenerate primers, DFBP1.F and DFBP3.R [15]. Thermal cycling was performed with an MJ Research DNA engine PTC-100 and the following parameters were used: after a 94°C for 3 min.…”

“…In mammals, most fucose-binding lectins identified so far belong to the Ctype family. Recently, a new family of lectins specific for fucose (F-type lectins) was described with members present in both prokaryotes and eukaryotes, including invertebrates and vertebrates [15]. This lectin family shares a characteristic sequence motif in the CRD, and a novel structural fold [18].…”

“…This lectin family shares a characteristic sequence motif in the CRD, and a novel structural fold [18]. In teleost fish, well-characterized members of this family are the serum lectins from the Japanese eel Anguilla japonica [16], sea bass Dicentrarchus labrax [17], European eel (A. anguilla) [18], and the striped bass Morone saxatilis fucose-binding protein [15].…”