The Sus operon: a model system for starch uptake by the human gut Bacteroidetes.
The Sus operon: a model system for starch uptake by the human gut Bacteroidetes.
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DOI：
10.1007/s00018-016-2242-x
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发表时间：
2016-07
期刊：
影响因子：
--
通讯作者：
Koropatkin NM
中科院分区：
文献类型：
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作者：
Foley MH;Cockburn DW;Koropatkin NM
人口密集的人类肠道中的常驻细菌必须有效地竞争碳水化合物营养。拟杆菌门是哺乳动物肠道中的优势细菌门，编码大量离散的多糖利用位点 (PUL)，这些位点被选择性激活以促进细胞表面的聚糖捕获。研究最深入的 PUL 编码聚糖摄取系统是多形拟杆菌的淀粉利用系统 (Sus)。 Sus 包括在细胞表面结合和降解淀粉所需的蛋白质，然后将寡糖转运穿过外膜，进一步解聚为周质中的葡萄糖。所有哺乳动物肠道拟杆菌都拥有类似的 Sus 系统，可靶向多种不同的聚糖。在这篇综述中，我们讨论了 B.thetaiotaomicron 的八种 Sus 蛋白的已知信息，这些蛋白定义了革兰氏阴性拟杆菌特有的类似 Sus 的营养获取范式。我们重点介绍了已充分表征的外膜蛋白 SusDEF 和 α-淀粉酶 SusG，它们各自具有独特的结构特征，使它们能够与细胞表面的淀粉相互作用。尽管这些蛋白质之间的淀粉结合位点明显冗余，但每种蛋白质在淀粉分解代谢过程中都具有独特的作用。此外，我们考虑了这些蛋白质如何在膜中动态相互作用和合作的已知信息，并提出了 Sus 外膜复合物形成的模型。
Resident bacteria in the densely populated human intestinal tract must efficiently compete for carbohydrate nutrition. The Bacteroidetes, a dominant bacterial phylum in the mammalian gut, encode a plethora of discrete polysaccharide utilization loci (PULs) that are selectively activated to facilitate glycan capture at the cell surface. The most well-studied PUL-encoded glycan-up-take system is the starch utilization system (Sus) of Bacteroides thetaiotaomicron. The Sus includes the requisite proteins for binding and degrading starch at the surface of the cell preceding oligosaccharide transport across the outer membrane for further depolymerization to glucose in the periplasm. All mammalian gut Bacteroidetes possess analogous Sus-like systems that target numerous diverse glycans. In this review, we discuss what is known about the eight Sus proteins of B. thetaiotaomicron that define the Sus-like paradigm of nutrient acquisition that is exclusive to the Gram-negative Bacteroidetes. We emphasize the well-characterized outer membrane proteins SusDEF and the α-amylase SusG, each of which have unique structural features that allow them to interact with starch on the cell surface. Despite the apparent redundancy in starch-binding sites among these proteins, each has a distinct role during starch catabolism. Additionally, we consider what is known about how these proteins dynamically interact and cooperate in the membrane and propose a model for the formation of the Sus outer membrane complex.