Chemosensory pathways represent a major prokaryotic signal transduction mechanism that is based on signal sensing by chemoreceptors. An essential feature of chemosensory pathways is the CheR and CheB mediated control of chemoreceptor methylation causing pathway adaptation. At their C-terminal extension the Tar and Tsr model chemoreceptors contain a pentapeptide that acts as an additional CheR and CheB binding site. The relevance of this pentapeptide is poorly understood since pentapeptide removal from Tar/Tsr causes receptor inactivation, whereas many other chemoreceptors do not require this pentapeptide for correct function. We report here a bioinformatic analysis of pentapeptide containing chemoreceptors. These receptors were detected in 11 bacterial phyla and represent approximately 10 % of all chemoreceptors. Pentapeptide containing chemoreceptors are mainly found in Gram-negative bacteria, are of low abundance in Gram-positive species and almost absent from archaea. Almost 50 % of TarH (Tar homologue) ligand binding domain containing chemoreceptors possess pentapeptides, whereas chemoreceptor families with other ligand binding domains are devoid of pentapeptides. The abundance of chemoreceptors with C-terminal pentapeptides correlated negatively with the number of chemoreceptor genes per genome. The consensus sequence reveals a negative net charge for many pentapeptides. Pentapeptide containing chemoreceptors are very abundant in the order Enterobacterales, particularly in the families Pectobacterium and Dickeya, where they represent about 50 % of the total number. In contrast, bacteria with primarily free living lifestyles have a reduced number of pentapeptides such as approximately 1 % for Pseudomonadales. It is proposed that pentapeptide function is related to mechanisms that permit host interaction.

化学感应途径代表了一种主要的原核信号转导机制，该机制基于化学感受器的信号感应。化学感觉途径的基本特征是CheR和CheB介导的化学感受器甲基化的控制，导致途径适应。Tar和Tsr模型的化学感受器在其C末端延伸处包含一个五肽，可充当其他CheR和CheB结合位点。由于从Tar / Tsr中除去五肽会导致受体失活，因此对该五肽的相关性了解甚少，而许多其他化学感受器不需要此五肽即可发挥正确的功能。我们在这里报告了含有化学感受器的五肽的生物信息学分析。在11个细菌门中检测到这些受体，约占所有化学感受器的10％。含有五肽的化学感受器主要存在于革兰氏阴性细菌中，在革兰氏阳性菌种中丰度较低，而古细菌中几乎不存在。几乎50％的TarH（包含同源物的化学感受器的Tar hmologue）配体结合域具有五肽，而具有其他配体结合域的化学感受器家族则不含五肽。具有C端五肽的化学感受器的丰度与每个基因组的化学感受器基因的数量呈负相关。共有序列揭示了许多五肽的负净电荷。含有五肽的化学感受器在肠杆菌科中非常丰富，特别是在果胶杆菌和迪卡科家族中，它们占总数的50％。相反，具有主要自由生活生活方式的细菌的五肽数量减少，例如假单胞菌约为1％。建议五肽功能与允许宿主相互作用的机制有关。