College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China/Key Laboratory of Integrated Management of Crop Diseases and Pests (Nanjing Agricultural University), Ministry of Education, Nanjing 210014, P.R. China.
Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, P.R. China.
Nucleic Acids Res. 2018 Oct 12;46(18):9276-9288. doi: 10.1093/nar/gky803.
Enzymes controlling intracellular second messengers in bacteria, such as c-di-GMP, often affect some but not other targets. How such specificity is achieved is understood only partially. Here, we present a novel mechanism that enables specific c-di-GMP-dependent inhibition of the antifungal antibiotic production. Expression of the biosynthesis operon for Heat-Stable Antifungal Factor, HSAF, in Lysobacter enzymogenes occurs when the transcription activator Clp binds to two upstream sites. At high c-di-GMP levels, Clp binding to the lower-affinity site is compromised, which is sufficient to decrease gene expression. We identified a weak c-di-GMP phosphodiesterase, LchP, that plays a disproportionately high role in HSAF synthesis due to its ability to bind Clp. Further, Clp binding stimulates phosphodiesterase activity of LchP. An observation of a signaling complex formed by a c-di-GMP phosphodiesterase and a c-di-GMP-binding transcription factor lends support to the emerging paradigm that such signaling complexes are common in bacteria, and that bacteria and eukaryotes employ similar solutions to the specificity problem in second messenger-based signaling systems.
细菌中控制细胞内第二信使（如 c-di-GMP）的酶通常会影响一些但不是其他靶标。这种特异性是如何实现的，目前仅部分了解。在这里，我们提出了一种新的机制，使特定的 c-di-GMP 依赖性抑制抗真菌抗生素的产生成为可能。当转录激活因子 Clp 结合到两个上游位点时，Lysobacter enzymogenes 中 Heat-Stable Antifungal Factor（HSAF）的生物合成操纵子表达。在高 c-di-GMP 水平下，Clp 与低亲和力位点的结合受到损害，这足以降低基因表达。我们鉴定出一种弱的 c-di-GMP 磷酸二酯酶 LchP，由于其能够结合 Clp，因此在 HSAF 合成中发挥了不成比例的高作用。此外，Clp 结合刺激了 LchP 的磷酸二酯酶活性。观察到由 c-di-GMP 磷酸二酯酶和 c-di-GMP 结合转录因子形成的信号复合物，支持了这样一种新兴范式，即这种信号复合物在细菌中很常见，并且细菌和真核生物在基于第二信使的信号系统中采用类似的方法来解决特异性问题。
