Carrington D M, Auffret A, Hanke D E
Nature. 1985;313(5997):64-7. doi: 10.1038/313064a0.
Lectins are proteins with multivalent carbohydrate-binding sites, which confer the ability to agglutinate. The seeds of legumes are particularly rich in lectins, for example, concanavalin A (Con A) comprises up to 15% of the protein in the cotyledons of jack bean (Canavalia ensiformis) seeds. The amino acid sequences of Con A and several other legume lectins have been partially or fully determined, and comparison of these sequences from different species reveals a circular homology (Fig. 1A); rearrangements within the genome have been suggested to explain this. We report here that the circular homology displayed by Con A is due to a post-translational transposition and ligation within the initial polypeptide. This type of modification has not been reported previously for eukaryotes, although it has been suggested to occur in bacteriophage lambda.
凝集素是具有多价碳水化合物结合位点的蛋白质，具有凝集能力。豆类种子中凝集素特别丰富，例如，伴刀豆球蛋白A（Con A）占刀豆（Canavalia ensiformis）种子子叶中蛋白质的15%。Con A和其他几种豆类凝集素的氨基酸序列已部分或完全确定，对不同物种的这些序列进行比较可发现环状同源性（图1A）；有人提出基因组内的重排来解释这一现象。我们在此报告，Con A所显示的环状同源性是由于初始多肽内的翻译后转座和连接。这种修饰类型以前在真核生物中尚未见报道，尽管有人认为在噬菌体λ中会发生。
