Fineran Peter C, Slater Holly, Everson Lee, Hughes Katie, Salmond George P C
Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, UK.
Mol Microbiol. 2005 Jun;56(6):1495-517. doi: 10.1111/j.1365-2958.2005.04660.x.
Summary Serratia sp. ATCC 39006 (39006) uses a complex hierarchical regulatory network allowing multiple inputs to be assessed before genes involved in secondary metabolite biosynthesis are expressed. This taxonomically ill-defined Serratia sp. produces a carbapenem antibiotic (Car; a beta-lactam) and a red pigmented antibiotic, prodigiosin (Pig; a tripyrrole), which are controlled by the smaIR quorum sensing (QS) locus. SmaR is a repressor of Pig and Car when levels of N-acyl- l-homoserine lactones, produced by SmaI, are low. In this study, we demonstrate direct DNA binding of purified SmaR to the promoter of the Car biosynthetic genes and abolition of this binding by the QS ligand. We have also identified multiple new secondary metabolite regulators. QS controls production of secondary metabolites, at least in part, by modulating transcription of three genes encoding regulatory proteins, including a putative response regulator of the GacAS two-component signalling system family, a novel putative adenylate cyclase and Rap (regulator of antibiotic and pigment). Mutations in another gene encoding a novel predicted global regulator, pigP, are highly pleiotropic; PigP has a significant "master" regulatory role in 39006 where it controls the transcription of six other regulators. The PigP protein and its homologues define a new family of regulators and are predicted to bind DNA via a helix-turn-helix domain. There are regulatory overlaps between the QS and PigP regulons that enable the information from different physiological cues to be funnelled into the control of secondary metabolite production.
摘要 粘质沙雷氏菌ATCC 39006（39006）利用一个复杂的分级调控网络，在参与次级代谢产物生物合成的基因表达之前，允许对多种输入信号进行评估。这种分类学上定义不明确的粘质沙雷氏菌产生一种碳青霉烯抗生素（Car；一种β-内酰胺）和一种红色色素抗生素灵菌红素（Pig；一种三吡咯），它们受smaIR群体感应（QS）位点控制。当由SmaI产生的N-酰基-L-高丝氨酸内酯水平较低时，SmaR是Pig和Car的阻遏物。在本研究中，我们证明了纯化的SmaR与Car生物合成基因启动子的直接DNA结合，以及QS配体对这种结合的消除。我们还鉴定了多个新的次级代谢产物调节因子。群体感应至少部分地通过调节三个编码调节蛋白的基因的转录来控制次级代谢产物的产生，这三个调节蛋白包括GacAS双组分信号系统家族的一个假定应答调节因子、一个新型假定腺苷酸环化酶和Rap（抗生素和色素调节因子）。另一个编码新型预测全局调节因子pigP的基因突变具有高度多效性；PigP在39006中具有重要的“主”调节作用，它控制其他六个调节因子的转录。PigP蛋白及其同源物定义了一个新的调节因子家族，并预计通过螺旋-转角-螺旋结构域结合DNA。群体感应和PigP调控子之间存在调节重叠，这使得来自不同生理信号的信息能够汇集到次级代谢产物产生的控制中。
