Individual lectin–carbohydrate interactions are usually of low affinity. However, high avidity is frequently attained by the multivalent presentation of glycans on biological surfaces coupled with the occurrence of high order lectin oligomers or tandem repeats of lectin domains in the polypeptide. F-type lectins are l-fucose binding lectins with a typical sequence motif, HX(26)RXDX(4)R/K, whose residues participate in l-fucose binding. We previously reported the presence of a few eukaryotic F-type lectin domains with partial sequence duplication that results in the presence of two l-fucose-binding sequence motifs. We hypothesized that such partial sequence duplication would result in greater avidity of lectin–ligand interactions. Inspired by this example from Nature, we attempted to engineer a bacterial F-type lectin domain from Streptosporangium roseum to attain avid binding by mimicking partial duplication. The engineered lectin demonstrated 12-fold greater binding strength than the wild-type lectin to multivalent fucosylated glycoconjugates. However, the affinity to the monosaccharide l-fucose in solution was similar and partial sequence duplication did not result in an additional functional l-fucose binding site. We also cloned, expressed and purified a Branchiostoma floridae F-type lectin domain with naturally occurring partial sequence duplication and confirmed that the duplicated region with the F-type lectin sequence motif did not participate in l-fucose binding. We found that the greater binding strength of the engineered lectin from S. roseum was instead due to increased oligomerization. We believe that this Nature-inspired strategy might be useful for engineering lectins to improve binding strength in various applications.

中文翻译：

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大自然启发的F型凝集素工程设计，可提高结合强度

各个凝集素与碳水化合物的相互作用通常亲和力低。然而，通过在生物表面上聚糖的多价呈递以及在多肽中出现高阶凝集素寡聚体或凝集素结构域的串联重复，常常获得高亲和力。F型凝集素是具有典型序列基序HX（26）RXDX（4）R / K的1-岩藻糖结合凝集素，其残基参与1-岩藻糖结合。我们以前报道了几个真核F型的存在凝集素与部分序列的重复结构域导致两个存在升-岩藻糖结合序列基序。我们假设这样的部分序列重复将导致凝集素-配体相互作用的更大亲合力。受到《自然》杂志的这个例子的启发，我们试图从玫瑰链霉菌中改造一个细菌F型凝集素结构域，以通过模仿部分重复来获得亲和力。经工程改造的凝集素显示出比野生型凝集素对多价岩藻糖基化糖缀合物的结合强度高12倍。然而，对溶液中的单糖1-岩藻糖的亲和力是相似的，并且部分序列重复没有导致额外的功能性1-岩藻糖结合位点。我们还克隆，表达和纯化了佛罗里达州的一个分支具有自然发生的部分序列重复的F型凝集素结构域，并证实具有F型凝集素序列基序的重复区域不参与1-岩藻糖结合。我们发现，来自玫瑰链霉菌的工程凝集素的更大的结合强度是由于增加的低聚。我们认为，这种受自然启发的策略可能对工程凝集素提高各种应用中的结合强度有用。