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

肠道微生物群在结肠健康和稳态中起着重要作用。有益细菌的生长可以 通过在人类饮食中给予益生元来促进。抗性淀粉是一种益生元， 优先促进特化细菌的生长，包括双歧杆菌。2型 抗性淀粉是未加工的颗粒状淀粉，由于其紧密堆积， 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 编码与淀粉颗粒组分结合并水解糖苷键的蛋白质。淀粉- 特异性碳水化合物结合模块（CBM）通常附加到糖苷水解酶家族13 （GH 13）结构域，其水解淀粉中的葡萄糖键。B。编码7个细胞外 含有GH 13的酶，包括BaAmy 7，其对生马铃薯和玉米淀粉具有高度活性。BaAmy7 编码四个预测的CBM，其中三个属于CBM家族先前显示结合生淀粉。这 该提案旨在了解BaAmy 7的作用机制，以及这四个方面的协调努力如何 CBM允许抗性淀粉作为底物。我假设，约束力和适当的空间安排， 四种CBM中的每一种都是最大催化活性所必需的。为了验证这个假设，我将（1）剖析角色 BaAmy 7的抗性淀粉水解中的单个CBM的结构排列和（2）阐明了BaAmy 7的抗性淀粉水解中的单个CBM的结构排列和（3）阐明了BaAmy 7的抗性淀粉水解中的单个CBM的结构排列。 BaAmy 7结构域。这些目标的完成将导致更好地了解分子特征， BaAmy 7在其水解抗性淀粉的能力方面是与众不同的。

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.