The role of carbohydrate binding module cooperation in BaAmy7 hydrolysis of resistant starch

肠道微生物区系在结肠健康和动态平衡中起着重要作用。有益细菌的生长可以 通过在人类饮食中添加益生元来促进。抗性淀粉是一种益生菌 优先促进专门化细菌的生长，包括青春型双歧杆菌。类型2 抗性淀粉是原始的颗粒状淀粉，由于其紧密包装，大多数酶都无法获得。 半结晶结构。为了分解和利用抗性淀粉作为营养源，细菌必须 编码与淀粉颗粒成分结合的蛋白质，并水解糖苷键。淀粉- 特定的碳水化合物结合模块(CBM)通常附加到糖苷水解酶家族13 (Gh13)结构域，它能分解淀粉中的葡萄糖键。B.青春期病毒编码7种胞外基因 含有GH13的酶包括BaAmy7，它对生土豆和玉米淀粉具有很高的活性。BaAmy7 编码四个预测的CBM，其中三个属于先前显示的与生淀粉结合的CBM家族。这 该提案旨在了解BaAmy7的作用机制以及这四个因素如何协调努力 CBMS允许抗性淀粉作为底物。我假设，约束和适当的空间安排 四种CBM中的每一种都是最大催化活性所必需的。为了检验这一假设，我将(1)剖析角色 在抗性淀粉被BaAmy7降解中的单个CBM和(2)阐明了 BaAmy7结构域。完成这些目标将导致更好地理解分子特征 让BaAmy7在水解抗性淀粉方面脱颖而出。

The gut microbiota plays a major role in colonic health and homeostasis. The growth of beneficial bacteria can be promoted by the administration of prebiotics in the human diet. Resistant starch is a prebiotic that preferentially promotes the growth of specialized bacteria, including Bifidobacterium adolescentis. Type 2 resistant starches are raw, granular starches that are inaccessible to most enzymes due to their tightly packed semi-crystalline structure. To break down and utilize resistant starch as a nutrient source, a bacterium must encode proteins that bind to the starch granule components and hydrolyze glycosidic linkages. Starch- specific carbohydrate binding modules (CBMs) are commonly appended to glycoside hydrolase family 13 (GH13) domains, which hydrolyze the glucose linkages in starch. B. adolescentis encodes seven extracellular GH13-containing enzymes including BaAmy7, which is highly active on raw potato and corn starch. BaAmy7 encodes four predicted CBMs, three of which belong to CBM families previously shown to bind raw starch. This proposal aims to understand the mechanism of action of BaAmy7 and how the coordinated effort of these four CBMs permits resistant starch as a substrate. I hypothesize that the binding and proper spatial arrangement of each of the four CBMs is required for maximal catalytic activity. To test this hypothesis, I will (1) dissect the role of individual CBMs in resistant starch hydrolysis by BaAmy7 and (2) elucidate the structural arrangement of BaAmy7 domains. Completion of these aims will lead to a better understanding of the molecular features that set apart BaAmy7 in its ability to hydrolyze resistant starch.