Department of Chemistry/Biochemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse, D-35032 Marburg, Germany.
Proc Natl Acad Sci U S A. 2010 Dec 28;107(52):22511-6. doi: 10.1073/pnas.1013210108. Epub 2010 Dec 13.
In the budding yeast Saccharomyces cerevisiae, self-recognition and the thereby promoted aggregation of thousands of cells into protective flocs is mediated by a family of cell-surface adhesins, the flocculins (Flo). Based on this social behavior FLO genes fulfill the definition of "greenbeard" genes, which direct cooperation toward other carriers of the same gene. The process of flocculation plays an eminent role in the food industry for the production of beer and wine. However, the precise mode of flocculin-mediated surface recognition and the exact structure of cognate ligands have remained elusive. Here, we present structures of the adhesion domain of a flocculin complexed to its cognate ligands derived from yeast high-mannose oligosaccharides at resolutions up to 0.95 Å. Besides a PA14-like architecture, the Flo5A domain reveals a previously undescribed lectin fold that utilizes a unique DcisD calcium-binding motif for carbohydrate binding and that is widely spread among pro- and eukaryotes. Given the high abundance of high-mannose oligosaccharides in yeast cell walls, the Flo5A structure suggests a model for recognition, where social non-self- instead of unsocial self-interactions are favored.
在 budding 酵母酿酒酵母中，自我识别以及由此促进的数千个细胞聚集成保护性絮体的过程是由一系列细胞表面黏附素（flocculin，Floc）介导的。基于这种社会行为，FLO 基因满足了“绿胡子”基因的定义，即指导对同一基因的其他载体的合作。絮凝过程在啤酒和葡萄酒生产的食品工业中起着重要作用。然而，絮凝素介导的表面识别的确切模式和同源配体的确切结构仍然难以捉摸。在这里，我们展示了与来自酵母高甘露糖寡糖的同源配体复合的絮凝素黏附结构域的结构，分辨率高达 0.95 Å。除了具有 PA14 样结构外，Flo5A 结构域还揭示了以前未描述的凝集素折叠，该折叠利用独特的 DcisD 钙结合基序进行碳水化合物结合，并且在原核生物和真核生物中广泛存在。鉴于酵母细胞壁中高甘露糖寡糖的高丰度，Flo5A 结构提示了一种识别模型，其中社会非自我相互作用而不是非社会自我相互作用是有利的。
