Analysis of the structural specificity of the lactose permease toward sugars.
Analysis of the structural specificity of the lactose permease toward sugars.
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DOI：
10.1016/s0021-9258(18)71576-7
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发表时间：
1989-09
期刊：
影响因子：
--
通讯作者：
S. Olsen;R. Brooker
中科院分区：
文献类型：
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作者：
S. Olsen;R. Brooker
研究了乳糖通透酶的糖特异性。游离半乳糖被证明竞争性抑制乳糖通透酶产生的aKi值为7.4 mM。这个值是几倍高于乳糖（1.3 mM）。各种其他单糖也表现出显着抑制乳糖转运。关于半乳糖环上沿着的−OH基团，其相对重要性为OH-3 > OH-4 > OH-6 > OH-2 > OH-1。一般来说，与β-连接的半乳糖苷相比，具有α-连接的半乳糖苷表现出显着更高的亲和力。半乳糖苷的糖苷配基部分的最佳尺寸是用含有己糖残基或苯环的糖苷配基达到的。糖苷配基的优选大小似乎是己糖、苯环>甲基>无糖苷配基的二糖>三糖。然而，无论是糖苷配基的特定结构，也不是它的相对疏水性似乎是渗透酶识别的重要因素。例如，疏水性β-硝基苯基半乳糖苷与乳糖（β-半乳糖苷）相比具有较低的亲和力，而α-硝基苯基半乳糖苷与蜜二糖（α-半乳糖苷）相比通常具有较高的亲和力。此外，当考虑苯环上硝基的位置时，没有看到一致的偏好。从这项工作中，提出了一个模型，它描绘了半乳糖苷的乳糖通透酶的结合。
The sugar specificity properties of the lactose permease were investigated. Free galactose was shown to competitively inhibit the lactose permease yielding aKivalue of 7.4 mM. This value was severalfold higher than the observedKmfor lactose (1.3 mM). A variety of other monosaccharides also showed significant inhibition of lactose transport. With regard to −OH groups along the galactose ring it appears that the relative importance is OH-3 > OH-4 > OH-6 > OH-2 > OH-1. In general, galactosides with α-linkages exhibited significantly higher affinities compared with their β-linked counterparts. An optimal size for the aglycone portion of the galactoside was reached with aglycones containing hexose residues or a benzene ring. The preferred size of the aglycone appears to be hexose, benzene ring > methyl group > no aglycone ≫ disaccharide > trisaccharide. However, neither the specific structure of the aglycone nor its relative hydrophobicity appeared to be important factors in permease recognition. For example, the hydrophobic β-nitrophenylgalactosides had lower affinities compared with lactose (a β-galactoside), whereas the α-nitrophenylgalactosides generally had higher affinities compared with melibiose (an a-galactoside). In addition, no consistent preference was seen when considering the location of the nitro group on the benzene ring. From this work, a model is presented which depicts the binding of galactosides to the lactose permease.