Ulitzur S, Kuhn J
Department of Food Engineering and Biotechnology, Technion-Israel Institute of Technology, Haifa.
J Biolumin Chemilumin. 1988 Apr-Jun;2(2):81-93. doi: 10.1002/bio.1170020205.
Luminescence in the marine bacterium, Vibrio fischeri, is regulated by a small molecule, the autoinducer. The transcription of the V. fischeri lux genes also requires a regulatory protein, (luxR), cAMP and CRP. We show that, apart from these components, the transcription of the PR lux operon is also controlled by the activity of sigma 32 (htpR protein). In luminescent Escherichia coli (E. coli/pChv1), as well as in different marine luminous bacteria and their naturally occurring dark (K) variants, the luminescence system can be induced by starvation under microaerophilic conditions. Heat shock also induces luminescence in htpR+ but not in htpR- strains of E. coli/pChv1. An htpR- mutant of E. coli containing pChv1 is very dim and its luminescence is not induced by starvation or heat shock. The addition of a plasmid bearing the gene for htpR+ into such cells restores their response to starvation and heat shock. Cells of wild type E. coli/pChv1 that have been starved or heat shocked respond to lower concentrations of V. fischeri inducer than untreated cells. These cultures also produce more extracellular inducer than untreated cells. Starvation, heat shock and the presence of sigma 32 do not induce luminescence in luxl deleted E. coli/pChv1 cells. SOS-inducing agents advance the onset of luminescence in both htpR+ and htpR- strains but not in luxl deleted E. coli/pChvi cells. DNA sequencing of the luxR-luxl region reveals the presence of a promoter region of the kind typical for sigma 32 at the beginning of the luxl gene. In addition we find a LexA protein-DNA binding site in the non-consensus sequence for the -35 region of the PR operon. It is proposed that the regulatory protein-inducer complex displaces the LexA protein and allows the transcription of the right operon. SOS-inducing agents result in proteolysis of LexA protein and advance the onset of luminescence. sigma 32 enhances the transcription from the PR operon and thus initiates a positive control circuit. It seems that sigma 32 is the major controlling element in determining the onset of luminescence both in vivo and in vitro.
海洋细菌费氏弧菌中的发光现象受一种小分子——自诱导物调控。费氏弧菌lux基因的转录还需要一种调控蛋白（luxR）、环磷酸腺苷（cAMP）和环腺苷酸受体蛋白（CRP）。我们发现，除了这些成分外，PR lux操纵子的转录还受σ32（htpR蛋白）活性的控制。在发光的大肠杆菌（E. coli/pChv1）以及不同的海洋发光细菌及其天然存在的暗（K）变体中，微需氧条件下的饥饿可诱导发光系统。热休克也能在htpR+的大肠杆菌/pChv1菌株中诱导发光，但在htpR-菌株中则不能。含有pChv1的大肠杆菌htpR-突变体发光很微弱，其发光不会因饥饿或热休克而诱导。将携带htpR+基因的质粒导入此类细胞可恢复它们对饥饿和热休克的反应。饥饿或热休克处理过的野生型大肠杆菌/pChv1细胞比未处理的细胞对更低浓度的费氏弧菌诱导物有反应。这些培养物产生的细胞外诱导物也比未处理的细胞多。饥饿、热休克和σ32的存在不会在luxl缺失的大肠杆菌/pChv1细胞中诱导发光。SOS诱导剂可提前htpR+和htpR-菌株的发光起始时间，但在luxl缺失的大肠杆菌/pChvi细胞中则不会。对luxR-luxl区域进行DNA测序发现在luxl基因起始处存在一个典型的σ32启动子区域。此外，我们在PR操纵子-35区域的非共有序列中发现了一个LexA蛋白-DNA结合位点。有人提出调控蛋白-诱导物复合物会取代LexA蛋白，从而使右侧操纵子得以转录。SOS诱导剂会导致LexA蛋白的蛋白水解并提前发光起始时间。σ32增强PR操纵子的转录，从而启动一个正调控回路。看来σ32是决定体内和体外发光起始的主要控制元件。
