THE RECOGNITION OF MALTODEXTRINS BY ESCHERICHIA-COLI
THE RECOGNITION OF MALTODEXTRINS BY ESCHERICHIA-COLI
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DOI：
10.1111/j.1432-1033.1980.tb04758.x
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发表时间：
1980-01-01
期刊：
影响因子：
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通讯作者：
FERENCI, T
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作者：
FERENCI, T
大肠杆菌可以积累 14C 标记的 (.alpha.1.fwdarw.4) 连接的 D-葡萄糖寡聚物直至麦芽七糖。较长的麦芽糖糊精不会被运输，也不会被用作碳源。太大而无法运输的麦芽糖糊精被完整的大肠杆菌的外膜结合。该结合是可饱和的（麦芽十糖的Kd=3×4μM）并且结合位点可由麦芽糖诱导。完全诱导后，每种细菌大约有 30,000 个位点。使用缺乏麦芽糖转运系统的各种成分的突变体，完整细菌对麦芽糖糊精的高亲和力结合被证明依赖于λ的存在。受体（外膜蛋白）和周质麦芽糖结合蛋白。可利用和不可利用的麦芽糖糊精具有相同的结合位点。麦芽十五糖是麦芽糖转运的竞争性抑制剂（Ki 1.5-2.5 μM）。周质麦芽糖结合蛋白易于与至少 2500 MW 的底物接触。无法转运大于麦芽七糖的糊精是由于大肠杆菌无法将大的底物从结合蛋白转移到细胞质，而不是缺乏通过外膜的通道。
E. coli can accumulate 14C-labeled (.alpha.1 .fwdarw. 4)-linked D-glucose oligomers up to maltoheptaose. Longer maltodextrins are not transported and are not utilized as C sources. Maltodextrins too large to be transported are bound by the outer envelope of intact E. coli. This binding is saturable (Kd for maltodecaose = 3 4 .mu.M) and the binding sites are inducible by maltose. Each bacterium has approximately 30,000 sites when fully induced. Using mutants devoid of various components of the maltose transport system, the high-affinity binding of maltodextrins by intact bacteria was shown to be dependent on the presence of .lambda. receptor (an outer membrane protein) and periplasmic maltose binding protein. The same binding sites are accessible to utilizable and non-utilizable maltodextrins. Maltodecapentaose is a competitive inhibitor of maltose transport (Ki 1.5-2.5 .mu.M). The periplasmic maltose binding protein is readily accessible to substrates of at least 2500 MW. The inability to transport dextrins larger than maltoheptaose is due to the inability of E. coli to transfer large substrates from the binding protein to the cytoplasm and not to lack of access through the outer membrane.