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【bio-news】Structure：肠道菌用结构识别控制淀粉分
多形类杆菌是人体肠道菌群中的主要成员之一，它是一类典型的多糖采集菌。多形类杆菌18%的基因组针对多糖的分解和利用。左图左上角代表这种微生物的淀粉利用系统（SUS），它是由糖苷酶，多糖蛋白的识别，以及运输蛋白构成的；右下角是Koropatkin等学者描述的SusD结构，它通过识别淀粉的螺旋结构与多糖结合。
人体的肠道中微生物可以执行一些不用基因组编码的功能，包括分解不能消化的膳食多聚糖。根据肠道菌群的处理能力，经过糖分解细菌的基因组分析可以确定了一些特定的多聚糖，研究这些多聚糖的输入和分解有助于人们确定其相关蛋白质的结构。在7月9日的《结构》（Structure）杂志上，Koropatkin等人描述了多形类杆菌结合、分解淀粉所涉及的一个蛋白质（SusD）的结构。这种独特的α-螺旋蛋白质包含一个弧形的芳香残基，它可以补充淀粉的天然螺旋结构，从而使这种构象可以有效地与麦芽七糖结合。此外，它还能够以强于线性结构的亲和力与环状低聚糖结合。
几个SusD蛋白质-低聚糖的复合物表明，可能有一种内在的识别配体的弹性结构，这种结构是由低聚糖的三维空间构象决定的，而不与复合糖的相互作用有关。
原始出处：
Structure，Vol 16, 1105-1115, 09 July 2008，Nicole M. Koropatkin, Thomas J. Smith
Starch Catabolism by a Prominent Human Gut Symbiont Is Directed by the Recognition of Amylose Helices
Nicole M. Koropatkin,1 Eric C. Martens,2 Jeffrey I. Gordon,2 and Thomas J. Smith1,
1 Donald Danforth Plant Science Center, St. Louis, MO 63132, USA
2 Center for Genome Sciences, Washington University in St. Louis School of Medicine, St. Louis, MO 63108, USA
Corresponding author
Thomas J. Smith
tsmith@danforthcenter.org
Summary
The human gut microbiota performs functions that are not encoded in our Homo sapiens genome, including the processing of otherwise undigestible dietary polysaccharides. Defining the structures of proteins involved in the import and degradation of specific glycans by saccharolytic bacteria complements genomic analysis of the nutrient-processing capabilities of gut communities. Here, we describe the atomic structure of one such protein, SusD, required for starch binding and utilization by Bacteroides thetaiotaomicron, a prominent adaptive forager of glycans in the distal human gut microbiota. The binding pocket of this unique α-helical protein contains an arc of aromatic residues that complements the natural helical structure of starch and imposes this conformation on bound maltoheptaose. Furthermore, SusD binds cyclic oligosaccharides with higher affinity than linear forms. The structures of several SusD/oligosaccharide complexes reveal an inherent ligand recognition plasticity dominated by the three-dimensional conformation of the oligosaccharides rather than specific interactions with the composite sugars. [标签:content1][标签:content2]
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作者:admin@医学,生命科学 2011-04-15 05:14
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