SUMMARY Chemoreceptors in bacteria detect a variety of signals and feed this information into chemosensory pathways that represent a major mode of signal transduction. The five chemoreceptors from Escherichia coli have served as traditional models in the study of this protein family. Genome analyses revealed that many bacteria contain much larger numbers of chemoreceptors with broader sensory capabilities. Chemoreceptors differ in topology, sensing mode, cellular location, and, above all, the type of ligand binding domain (LBD). Here, we highlight LBD diversity using well-established and emerging model organisms as well as genomic surveys. Nearly a hundred different types of protein domains that are found in chemoreceptor sequences are known or predicted LBDs, but only a few of them are ubiquitous. LBDs of the same class recognize different ligands, and conversely, the same ligand can be recognized by structurally different LBDs; however, recent studies began to reveal common characteristics in signal-LBD relationships. Although signals can stimulate chemoreceptors in a variety of different ways, diverse LBDs appear to employ a universal transmembrane signaling mechanism. Current and future studies aim to establish relationships between LBD types, the nature of signals that they recognize, and the mechanisms of signal recognition and transduction.

小结细菌中的化学感受器检测各种信号并将此信息馈送到代表信号转导主要模式的化学感应通路中。大肠杆菌的五种化学感受器已作为该蛋白质家族研究的传统模型。基因组分析表明，许多细菌含有数量多得多的化学感受器，具有更广泛的感觉能力。化学感受器在拓扑结构、传感模式、细胞位置以及最重要的配体结合域 (LBD) 类型方面有所不同。在这里，我们使用成熟的和新兴的模式生物以及基因组调查来强调 LBD 的多样性。在化学感受器序列中发现的近百种不同类型的蛋白质结构域是已知或预测的 LBD，但其中只有少数是普遍存在的。同一类别的LBD识别不同的配体，反之，相同的配体可以被结构不同的LBD识别；然而，最近的研究开始揭示信号-LBD 关系中的共同特征。尽管信号可以以多种不同方式刺激化学感受器，但不同的 LBD 似乎采用通用的跨膜信号机制。当前和未来的研究旨在建立 LBD 类型、它们识别的信号的性质以及信号识别和转导机制之间的关系。