F-type lectins are phylogenetically widespread but selectively distributed fucose-binding lectins with L-fucose- and calcium-binding sequence motifs and an F-type lectin fold. Bacterial F-type lectin domains frequently occur in tandem with various protein domains in diverse architectures, indicating a possible role in directing enzyme activities or other biological functions to distinct fucosylated niches. Here, we report the biochemical characterization of a Streptosporangium roseum protein containing an F-type lectin domain in tandem with an NPCBM-associated domain and a family GH 29A alpha-l-fucosidase domain. We show that the F-type lectin domain of this protein recognizes fucosylated glycans in both α and β linkages but has high affinity for a Fuc-α-1,2-Gal motif and that the alpha-l-fucosidase domain displays hydrolytic activity on glycan substrates with α1-2 and α1-4 linked fucose. We also show that the F-type lectin domain does not have any effect on the activity of the cis-positioned alpha-l-fucosidase domain with the synthetic substrate, 4-Methylumbelliferyl-alpha-l-fucopyranoside or on inhibition of this activity by l-fucose or deoxyfuconojirimycin hydrochloride. However, the F-type lectin domain together with the NPCBM-associated domain enhances the activity of the cis-positioned alpha-l-fucosidase domain for soluble fucosylated oligosaccharide substrates. While there are many reports of glycoside hydrolase activity towards insoluble and soluble polysaccharides being enhanced by cis-positioned carbohydrate binding modules on the polypeptide, this is the first report, to our knowledge, of enhancement of activity towards aqueous, freely diffusible, small oligosaccharides. We propose a model involving structural stabilization and a bind-and-jump action mediated by the F-type lectin domain to rationalize our findings.

中文翻译：

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一F型凝集素结构域指导的活性Streptosporangium霉α-升-fucosidase

F型凝集素在系统发育上广泛分布，但有选择地分布具有L-岩藻糖和钙结合序列基序和F型凝集素折叠的岩藻糖结合凝集素。细菌F型凝集素结构域经常与多种蛋白质结构域中的各种蛋白质结构串联在一起，表明在将酶活性或其他生物学功能引导至不同的岩藻糖基化壁ni中可能发挥作用。这里，我们报告一个的生物化学表征Streptosporangium霉含有串联F型凝集素结构域与NPCBM相关结构域和家族GH 29A的α-蛋白升-岩藻糖苷酶结构域。我们表明，该蛋白的F型凝集素结构域在α和β键均识别岩藻糖基化聚糖，但对Fuc-α-1,2-Gal基序具有高亲和力，并且α- 1-岩藻糖苷酶结构域在具有α1-2和α1-4的岩藻糖连接的聚糖底物。我们还显示，F型凝集素结构域对具有合成底物4-甲基伞形酮-α- 1-岩藻糖苷的顺式α- 1-岩藻糖苷酶结构域的活性或通过抑制该活性没有任何影响。l-岩藻糖或脱氧岩藻糖霉素盐酸盐。但是，F型凝集素结构域与NPCBM相关结构域一起增强了顺式的活性。-positioned的α-升可溶性岩藻糖化的寡糖底物-fucosidase域。尽管有许多报道说多肽上的顺式碳水化合物结合模块增强了糖苷水解酶对不溶和可溶多糖的活性，但据我们所知，这是关于增强对水，可自由扩散的小寡糖的活性的第一个报道。我们提出了一个模型，该模型涉及结构稳定和由F型凝集素结构域介导的结合和跳跃作用，以使我们的发现合理化。