F-19 NUCLEAR-MAGNETIC-RESONANCE STUDIES OF AQUEOUS AND TRANSMEMBRANE RECEPTORS - EXAMPLES FROM THE ESCHERICHIA-COLI CHEMOSENSORY PATHWAY
F-19 NUCLEAR-MAGNETIC-RESONANCE STUDIES OF AQUEOUS AND TRANSMEMBRANE RECEPTORS - EXAMPLES FROM THE ESCHERICHIA-COLI CHEMOSENSORY PATHWAY
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DOI：
10.1016/s0006-3495(92)81787-3
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发表时间：
1992-04-01
影响因子：
3.4
通讯作者：
SCHERRER, J
中科院分区：
文献类型：
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作者：
FALKE, JJ;LUCK, LA;SCHERRER, J
图1大肠杆菌的立体α-碳骨架结构。coli D-半乳糖和D-葡萄糖受体（8）。实心环表示糖裂中结合的D-葡萄糖分子，十字表示金属位点中的Ca（II）离子。图中还显示了5个trp和7个phe位置，它们用作“9 F-标记位点。在NMR时间尺度上的区域（7 ms），可能是由于附近的脯氨酸231的顺反异构化。这种结构异质性是高度局部化的，因为它在糖和Ca（II）位点内不会引起可检测的影响（3）。铰链裂缝模型的一个简单测试是监测5 F-trp 183的溶液暴露，它被隔离在封闭的裂缝中，但如果裂缝基本上打开，则应该可以接触到本体溶液。三价镧系元素Gd（III）（S= 7/2）是用于此目的的合适的顺磁探针，因为它显著地加宽了它所接近的核的NMR共振，与分离的倒数六次方（r）成比例：
FIGURE 1 Stereo a-carbon backbone structure of the E. coli D-galac-tose and D-glucose receptor (8). The solid ring indicates the bound D-glucose molecule in the sugar cleft, and the cross denotes the Ca (II) ion in the metal site. Also shown are the five trp and seven phe positions which serve as' 9F-labeling sites. region on the NMR timescale (7 ms), perhaps due to cis-trans isomerization of nearby proline 231. This struc-tural heterogeneity is highly localized because it causes no detectable effects within the sugar and Ca (II) sites (3).A simple test of the hinged cleft model is to monitor the solution exposure of 5F-trp 183, which is seques-tered in the closed cleft, but should become accessible to the bulk solution if the cleft opens substantially. The trivalent lanthanide Gd (III)(S= 7/2) is a suitable paramagnetic probe for this purpose because it signifi-cantly broadens the NMR resonance of a nucleus it approaches, in proportion to the inverse sixth power of the separation (r):