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首页> 外文期刊>Acta crystallographica. Section D, Structural biology. >Crystal structures of Escherichia coli branching enzyme in complex with cyclodextrins
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Crystal structures of Escherichia coli branching enzyme in complex with cyclodextrins

机译：大肠杆菌分支的晶体结构与环糊精酶在复杂

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摘要

Branching enzyme (BE) is responsible for the third step in glycogen/starch biosynthesis. It catalyzes the cleavage of alpha-1,4 glucan linkages and subsequent reattachment to form alpha-1,6 branch points. These branches are crucial to the final structure of glycogen and starch. The crystal structures of Escherichia coli BE (EcBE) in complex with alpha-, beta- and gamma-cyclodextrin were determined in order to better understand substrate binding. Four cyclodextrin-binding sites were identified in EcBE; they were all located on the surface of the enzyme, with none in the vicinity of the active site. While three of the sites were also identified as linear polysaccharide-binding sites, one of the sites is specific for cyclodextrins. In previous work three additional binding sites were identified as exclusively binding linear malto-oligosaccharides. Comparison of the binding sites shed light on this apparent specificity. Binding site IV is located in the carbohydrate-binding module 48 (CBM48) domain of EcBE and superimposes with the cyclodextrin-binding site found in the CBM48 domain of 5'-AMP-activated protein kinase (AMPK). Comparison of these sites shows the similarities and differences in the two binding modes. While some of the binding sites were found to be conserved between branching enzymes of different organisms, some are quite divergent, indicating both similarities and differences between oligosaccharide binding in branching enzymes from various sources.
机译：分支酶(是)负责第三糖原、淀粉生物合成。催化裂解的alpha - 4葡聚糖联系和随后的回贴alpha - 6分支点。糖原的最终结构和关键淀粉。杆菌(EcBE)在复杂与α-,β-gamma-cyclodextrin是为了决定更好地理解衬底绑定。cyclodextrin-binding网站被确定EcBE;酶,与附近的活跃网站。确认为线性polysaccharide-binding网站,一个网站是特定的环糊精。结合位点被认定为完全线性malto-oligosaccharides绑定。结合位点的阐明这个明显特异性。48 (CBM48)域carbohydrate-binding模块EcBE和添加CBM48 cyclodextrin-binding网站找到域的5 ' -AMP-activated蛋白激酶(AMPK)。这些网站的比较显示了相似之处和差异在两个绑定模式。结合位点被发现守恒的分支酶之间的不同生物,一些很发散,指示这两个之间的相似点和不同点低聚糖绑定在分支酶各种各样的来源。

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