School of Life Sciences and Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, Hubei, People's Republic of China.
School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, Australia.
J Bacteriol. 2018 Oct 10;200(21). doi: 10.1128/JB.00436-18. Print 2018 Nov 1.
Two cAMP receptor proteins (CRPs), Sycrp1 (encoded by ) and Sycrp2 (encoded by ), exist in the cyanobacterium sp. strain PCC 6803. Previous studies have demonstrated that Sycrp1 has binding affinity for cAMP and is involved in motility by regulating the formation of pili. However, the function of Sycrp2 remains unknown. Here, we report that disruption results in the loss of motility of sp. PCC 6803, and that the phenotype can be recovered by reintroducing the gene into the genome of -disrupted mutants. Electron microscopy showed that the -disrupted mutant lost the pilus apparatus on the cell surface, resulting in a lack of cell motility. Furthermore, the transcript level of the operon (essential for cell motility and regulated by the cAMP receptor protein Sycrp1) was markedly decreased in -disrupted mutants compared with the wild-type strain. Moreover, yeast two-hybrid analysis and a pulldown assay demonstrated that Sycrp2 interacted with Sycrp1 to form a heterodimer and that Sycrp1 and Sycrp2 interacted with themselves to form homodimers. Gel mobility shift assays revealed that Sycrp1 specifically binds to the upstream region of Together, these findings indicate that in sp. PCC 6803, Sycrp2 regulates the formation of pili and cell motility by interacting with Sycrp1. cAMP receptor proteins (CRPs) are widely distributed in cyanobacteria and play important roles in regulating gene expression. Although many cyanobacterial species have two cAMP receptor-like proteins, the functional links between them are unknown. Here, we found that Sycrp2 in the cyanobacterium sp. strain PCC 6803 is essential for twitching motility and that it interacts with Sycrp1, a known cAMP receptor protein involved with twitching motility. Our findings indicate that the two cAMP receptor-like proteins in cyanobacteria do not have functional redundancy but rather work together.
两种 cAMP 受体蛋白（CRPs），Sycrp1（由 编码）和 Sycrp2（由 编码），存在于蓝藻 PCC 6803 中。先前的研究表明，Sycrp1 对 cAMP 具有结合亲和力，并通过调节菌毛的形成参与运动。然而，Sycrp2 的功能仍然未知。在这里，我们报告说 的缺失导致 sp. PCC 6803 的运动性丧失，并且可以通过将 基因重新引入 -缺失突变体的基因组中来恢复表型。电子显微镜显示，-缺失突变体失去了细胞表面的菌毛装置，导致细胞运动性丧失。此外，与野生型菌株相比，-缺失突变体中 操纵子（对细胞运动至关重要并受 cAMP 受体蛋白 Sycrp1 调节）的转录水平显着降低。此外，酵母双杂交分析和下拉测定表明，Sycrp2 与 Sycrp1 相互作用形成异二聚体，并且 Sycrp1 和 Sycrp2 相互作用形成同源二聚体。凝胶迁移率变动分析显示，Sycrp1 特异性结合 的上游区域。综上所述，这些发现表明，在 sp. PCC 6803 中，Sycrp2 通过与 Sycrp1 相互作用来调节菌毛的形成和细胞运动。cAMP 受体蛋白（CRPs）广泛分布在蓝细菌中，在调节基因表达中起重要作用。尽管许多蓝细菌物种具有两种 cAMP 受体样蛋白，但它们之间的功能联系尚不清楚。在这里，我们发现蓝藻 PCC 6803 中的 Sycrp2 对于蠕动运动是必不可少的，并且它与已知参与蠕动运动的 cAMP 受体蛋白 Sycrp1 相互作用。我们的研究结果表明，蓝细菌中的两种 cAMP 受体样蛋白没有功能冗余，而是协同工作。
