Pottathil Mridula, Lazazzera Beth A
Department of Microbiology, Immunology, and Molecular Genetics, University of California Los Angeles, 1602 Molecular Sciences Building, 405 Hilgard Avenue, Los Angeles, CA 90095, USA.
Front Biosci. 2003 Jan 1;8:d32-45. doi: 10.2741/913.
In the field of cell-cell communication, an emerging class of extracellular signaling peptides that function intracellularly has been identified in Gram-positive bacteria. One illustrative member of this group is the Phr family of extracellular signaling peptides of Bacillus subtilis. The Phr signaling peptides are secreted by the bacterium, and then, despite the presence of intracellular peptidases, they are actively transported into the cell where they interact with intracellular receptors to regulate gene expression. The intracellular receptors are members of a family of aspartyl-phosphate phosphatases, the Rap phosphatases. These phosphatases cause the dephosphorylation of response regulator proteins, ubiquitous regulatory proteins in bacteria. Immediately downstream of the genes for the Rap phosphatases are the genes for the Phr peptides, forming rap phr signaling cassettes. There are at least seven rap phr signaling cassettes in B. subtilis, and the genome sequence of other Gram-positive, endospore-forming bacteria suggests that similar cassettes may also function in these bacteria. In B. subtilis, the rap phr cassettes regulate sporulation, genetic competence, and genes comprising the quorum response (i.e. the response to high cell density). This review will address the mechanism of extracellular Phr signaling peptide production, transport, response, and their role in quorum sensing.
在细胞间通讯领域，已在革兰氏阳性菌中鉴定出一类新兴的在细胞内发挥作用的细胞外信号肽。这一类别的一个典型成员是枯草芽孢杆菌的细胞外信号肽Phr家族。Phr信号肽由细菌分泌，然后，尽管存在细胞内肽酶，它们仍被主动转运到细胞内，在那里它们与细胞内受体相互作用以调节基因表达。细胞内受体是天冬氨酰 - 磷酸磷酸酶家族（Rap磷酸酶）的成员。这些磷酸酶导致响应调节蛋白（细菌中普遍存在的调节蛋白）去磷酸化。Rap磷酸酶基因的紧邻下游是Phr肽的基因，形成rap phr信号盒。枯草芽孢杆菌中至少有七个rap phr信号盒，其他革兰氏阳性产芽孢细菌的基因组序列表明，类似的信号盒可能在这些细菌中也发挥作用。在枯草芽孢杆菌中，rap phr信号盒调节芽孢形成、遗传感受态以及构成群体感应（即对高细胞密度的响应）的基因。本综述将探讨细胞外Phr信号肽的产生、转运、响应机制及其在群体感应中的作用。
