Oligosaccharide substrate binding in Escherichia coli maltodextrin phosphorylase
Oligosaccharide substrate binding in Escherichia coli maltodextrin phosphorylase
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DOI：
10.1038/nsb0597-405
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发表时间：
1997-05
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影响因子：
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通讯作者：
M. O’Reilly;K. Watson;R. Schinzel;D. Palm;L. Johnson
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文献类型：
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作者：
M. O’Reilly;K. Watson;R. Schinzel;D. Palm;L. Johnson
E.与低聚糖共结晶的Colimaltodextrin磷酸化酶已在3.0 nm分辨率下溶解，提供了结合在α-葡聚糖磷酸化酶催化位点的低聚糖的第一个结构。诱导配合机制将两个域跨催化位点隧道聚集在一起。一个堆叠之间的相互作用的葡萄糖基残基和芳香族基团的酪氨酸残基在一个子网站远程（8个）从催化位点提供了一个关键因素，在底物识别;突变的这个残基丙氨酸降低thekcat/Km的104。外推的结果，以底物结合整个网站的攻击磷酸化表明可能改变糖苷扭转角从他们的首选值，改变似乎是重要的催化机制。
The crystal structure ofE. colimaltodextrin phosphorylase co-crystallized with an oligosaccharide has been solved at 3.0 Å resolution, providing the first structure of an oligosaccharide bound at the catalytic site of an α-glucan phosphorylase. An induced fit mechanism brings together two domains across the catalytic site tunnel. A stacking interaction between the glucosyl residue and the aromatic group of a tyrosine residue at a sub-site remote (8 Å) from the catalytic site provides a key element in substrate recognition; mutation of this residue to Ala decreases thekcat/Kmby 104. Extrapolation of the results to substrate binding across the site of attack by phosphorolysis indicates a likely alteration in the glycosidic torsion angles from their preferred values, an alteration that appears to be important for the catalytic mechanism.