Wright Jesse S, Lyon Gholson J, George Elizabeth A, Muir Tom W, Novick Richard P
Molecular Pathogenesis Program and Department of Microbiology and Medicine, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA.
Proc Natl Acad Sci U S A. 2004 Nov 16;101(46):16168-73. doi: 10.1073/pnas.0404039101. Epub 2004 Nov 4.
Two-component systems represent the most widely used signaling paradigm in living organisms. Encoding the prototypical two-component system in Gram-positive bacteria, the staphylococcal agr (accessory gene regulator) operon uses a polytopic receptor, AgrC, activated by an autoinducing peptide (AIP), to coordinate quorum sensing with the global synthesis of virulence factors. The agr locus has undergone evolutionary divergence, resulting in the formation of several distinct inter- and intraspecies specificity groups, such that most cross-group AIP-receptor interactions are mutually inhibitory. We have exploited this natural diversity by constructing and analyzing AgrC chimeras generated by exchange of intradomain segments between receptors of different agr groups. Functional chimeras fell into three general classes: receptors with broadened specificity, receptors with tightened specificity, and receptors that lack activation specificity. Testing of these chimeric receptors against a battery of AIP analogs localized the primary ligand recognition site to the receptor distal subdomain and revealed that the AIPs bind primarily to a putative hydrophobic pocket in the receptor. This binding is mediated by a highly conserved hydrophobic patch on the AIPs and is an absolute requirement for interactions in self-activation and cross-inhibition of the receptors. It is suggested that this recognition scheme provides the fundamental basis for agr activation and interference.
双组分系统是生物体内使用最广泛的信号传导模式。葡萄球菌附属基因调节因子（agr）操纵子编码革兰氏阳性菌中的典型双组分系统，它利用一种由自诱导肽（AIP）激活的多跨膜受体AgrC来协调群体感应与毒力因子的整体合成。agr基因座经历了进化分化，导致形成了几个不同的种间和种内特异性组，因此大多数跨组AIP-受体相互作用是相互抑制的。我们通过构建和分析由不同agr组受体之间的结构域内片段交换产生的AgrC嵌合体，利用了这种自然多样性。功能性嵌合体分为三大类：特异性拓宽的受体、特异性收紧的受体以及缺乏激活特异性的受体。用一系列AIP类似物对这些嵌合受体进行测试，将主要配体识别位点定位到受体远端亚结构域，并揭示AIP主要结合到受体中一个假定的疏水口袋。这种结合由AIP上一个高度保守的疏水区域介导，是受体自激活和交叉抑制相互作用的绝对必要条件。有人提出，这种识别模式为agr激活和干扰提供了基本基础。
