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首页> 外文期刊>Journal of bacteriology >Analysis of Residues Determining Specificity of Vibrio cholerae TonB1 for Its Receptors
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Analysis of Residues Determining Specificity of Vibrio cholerae TonB1 for Its Receptors

机译：确定霍乱弧菌TonB1受体特异性的残基分析

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In gram-negative organisms, high-affinity transport of iron substrates requires energy transduction to specific outer membrane receptors by the TonB-ExbB-ExbD complex. Vibrio cholerae encodes two TonB proteins, one of which, TonB1, recognizes only a subset of V. cholerae TonB-dependent receptors and does not facilitate transport through Escherichia coli receptors. To investigate the receptor specificity exhibited by V. cholerae TonB1, chimeras were created between V. cholerae TonB1 and E. coli TonB. The activities of the chimeric TonB proteins in iron utilization assays demonstrated that the C-terminal one-third of either TonB confers the receptor specificities associated with the full-length TonB. Single-amino-acid substitutions near the C terminus of V. cholerae TonB1 were identified that allowed TonB1 to recognize E. coli receptors and at least one V. cholerae TonB2-dependent receptor. This indicates that the very C-terminal end of V. cholerae TonB1 determines receptor specificity. The regions of the TonB-dependent receptors involved in specificity for a particular TonB protein were investigated in experiments involving domain switching between V. cholerae and E. coli receptors exhibiting different TonB specificities. Switching the conserved TonB box heptapeptides at the N termini of these receptors did not alter their TonB specificities. However, replacing the amino acid immediately preceding the TonB box in E. coli receptors with an aromatic residue allowed these receptors to use V. cholerae TonB1. Further, site-directed mutagenesis of the TonB box ?1 residue in a V. cholerae TonB2-dependent receptor demonstrated that a large hydrophobic amino acid in this position promotes recognition of V. cholerae TonB1. These data suggest that the TonB box ?1 position controls productive interactions with V. cholerae TonB1.
机译：在革兰氏阴性生物中，铁底物的高亲和力运输需要通过TonB-ExbB-ExbD复合体将能量转导至特定的外膜受体。 霍乱弧菌编码两个TonB蛋白，其中一个TonB1仅识别 V 的一个子集。 霍乱 TonB依赖性受体，不促进通过大肠杆菌受体的转运。研究 V 表现出的受体特异性。 霍乱 TonB1，在 V 之间创建了嵌合体。 霍乱 TonB1和 E 。 大肠杆菌 TonB。嵌合的TonB蛋白在铁利用试验中的活性表明，任一TonB的C端三分之一都赋予了与全长TonB相关的受体特异性。 V 的C末端附近的单氨基酸取代。鉴定出霍乱 TonB1，从而使TonB1识别 E 。 大肠杆菌受体和至少一种 V 。 霍乱 TonB2依赖性受体。这表明 V 的正C端。 霍乱 TonB1决定受体的特异性。在涉及 V 之间域切换的实验中，研究了与特定TonB蛋白特异性相关的TonB依赖受体区域。 霍乱和 E 。 大肠杆菌受体表现出不同的TonB特异性。在这些受体的N末端切换保守的TonB盒七肽不会改变它们的TonB特异性。但是，替换 E 中TonB框之前的氨基酸。具有芳香族残基的 coli 受体允许这些受体使用 V 。 霍乱 TonB1。此外，在 V 中的TonB框β1残基的定点诱变。 霍乱 TonB2依赖性受体表明，该位置的大量疏水氨基酸可促进 V 的识别。 霍乱 TonB1。这些数据表明，TonB框？1的位置控制着与 V 的有效相互作用。 霍乱 TonB1。

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