Al Atalah Bassam, Vanderschaeghe Dieter, Bloch Yehudi, Proost Paul, Plas Kirsten, Callewaert Nico, Savvides Savvas N, Van Damme Els J M
Biol Chem. 2014 Apr;395(4):413-24. doi: 10.1515/hsz-2013-0267.
OrysaEULD1A is one of the five EUL genes in rice (Oryza sativa) encoding a putative carbohydrate-binding protein belonging to the family of Euonymus related lectins (EUL). The OrysaEULD1A sequence comprises two highly similar EUL domains (91% sequence similarity and 72% sequence identity) separated by a 23 amino acid linker sequence and preceded by a 19 amino acid N-terminal sequence. In the present study, the full-length protein OrysaEULD1A as well as its individual domains OrysaEULD1A domain 1 and 2 were expressed in Pichia pastoris. After purification of the recombinant proteins, their carbohydrate-binding specificity was analyzed and compared. Interestingly, all recombinant lectins showed clear specificity towards galactosylated structures. Furthermore, all recombinant proteins agglutinated red blood cells, indicating that the full-length protein OrysaEULD1A and its domains are true lectins. These results taken together with data previously reported for single-domain EUL proteins indicate that although the amino acids--responsible for the formation of the carbohydrate-binding site--are identical for all EUL proteins in rice, these lectins show different carbohydrate specificities. This promiscuity of the carbohydrate-binding site can be attributed to gene divergence.
OrysaEULD1A是水稻（Oryza sativa）中五个EUL基因之一，编码一种假定的碳水化合物结合蛋白，属于卫矛相关凝集素（EUL）家族。OrysaEULD1A序列包含两个高度相似的EUL结构域（序列相似性为91%，序列同一性为72%），由一个23个氨基酸的连接序列隔开，前面有一个19个氨基酸的N端序列。在本研究中，全长蛋白OrysaEULD1A及其单个结构域OrysaEULD1A结构域1和2在毕赤酵母中表达。重组蛋白纯化后，分析并比较了它们的碳水化合物结合特异性。有趣的是，所有重组凝集素对糖基化结构都表现出明显的特异性。此外，所有重组蛋白都能凝集红细胞，表明全长蛋白OrysaEULD1A及其结构域是真正的凝集素。这些结果与先前报道的单结构域EUL蛋白的数据一起表明，尽管水稻中所有EUL蛋白负责形成碳水化合物结合位点的氨基酸相同，但这些凝集素表现出不同的碳水化合物特异性。碳水化合物结合位点的这种混杂性可归因于基因分歧。
