Differential recognition of Staphylococcus aureus quorum-sensing signals depends on both extracellular loops 1 and 2 of the transmembrane sensor AgrC
Differential recognition of Staphylococcus aureus quorum-sensing signals depends on both extracellular loops 1 and 2 of the transmembrane sensor AgrC
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DOI：
10.1016/j.jmb.2008.06.018
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发表时间：
2008-08-29
影响因子：
5.6
通讯作者：
Williams, Paul
中科院分区：
文献类型：
--
作者：
Jensen, Rasmus O.;Winzer, Klaus;Williams, Paul
金黄色葡萄球菌的毒力是通过依赖于agr的群体感应来调节的，在群体感应中，一个自身诱导肽(AIP)激活了一种组氨酸蛋白激酶--AGRC。它们通常都是含有7到9个氨基酸残基的硫代内酯，其中中心半胱氨酸的硫醇与C末端氨基酸残基的α-羧基相连。金黄色葡萄球菌agr基因座的分化使得四个不同金黄色葡萄球菌agr组的AIP自我激活但交叉抑制。因此，尽管agr系统在葡萄球菌中是保守的，但它经历了显著的进化分化，从而为了保留功能，任何改变AIP结构的AIP编码基因(AgrD)都必须伴随着AGRC受体的相应变化。由于AIP-1和AIP-4只有一个氨基酸的差异，我们比较了AIP-1和AIP-4的跨膜拓扑结构，以确定参与AIP识别的氨基酸残基。由于预测的三个胞外环中只有两个显示出氨基酸差异，因此使用定点突变来单独或组合交换每个环中的关键氨基酸残基AGRC1和AGC4。构建了一种新型的基于lux的agrP3报告基因融合，以评估突变的agrP3受体的反应。结果表明，虽然AIP-1和AIP-4的识别主要依赖于环2上的三个氨基酸残基，但环1对于同源空气激活受体是必不可少的。此外，agc1环2上的单个突变导致(Ala5)AIP-1从有效的拮抗剂转变为激活剂，本质上导致了一个新的AIP基团的被迫进化。综上所述，我们的数据表明，环2构成了预测的疏水口袋，与AIP硫代内酯环结合，而外环氨基酸尾部与环I相互作用，促进受体激活。(C)2008爱思唯尔有限公司。保留所有权利。
Virulence in Staphylococcus aureus is regulated via agr-dependent quorum sensing in which an autoinducing peptide (AIP) activates AgrC, a histidine protein kinase. All's are usually thiolactones containing seven to nine amino acid residues in which the thiol of the central cysteine is linked to the alpha-carboxyl of the C-terminal amino acid residue. The staphylococcal agr locus has diverged such that the AIPs of the four different S. aureus agr groups self-activate but cross-inhibit. Consequently, although the agr system is conserved among the staphylococci, it has undergone significant evolutionary divergence whereby to retain functionality, any changes in the AIP-encoding gene (agrD) that modifies AIP structure must be accompanied by corresponding changes in the AgrC receptor. Since AIP-1 and AIP-4 only differ by a single amino acid, we compared the transmembrane topology of AgrC1 and AgrC4 to identify amino acid residues involved in AIP recognition. As only two of the three predicted extracellular loops exhibited amino acid differences, site-specific mutagenesis was used to exchange the key AgrC1 and AgrC4 amino acid residues in each loop either singly or in combination. A novel lux-based agrP3 reporter gene fusion was constructed to evaluate the response of the mutated AgrC receptors. The data obtained revealed that while differential recognition of AIP-1 and AIP-4 depends primarily on three amino acid residues in loop 2, loop 1 is essential for receptor activation by the cognate AIR Furthermore, a single mutation in the AgrC1 loop 2 resulted in conversion of (Ala5)AIP-1 from a potent antagonist to an activator, essentially resulting in the forced evolution of a new AIP group. Taken together, our data indicate that loop 2 constitutes the predicted hydrophobic pocket that binds the AIP thiolactone ring while the exocyclic amino acid tail interacts with loop I to facilitate receptor activation. (c) 2008 Elsevier Ltd. All rights reserved.