AI-2 (Autoinducer-2) protein was verified in a large number of species and the AI-2 Quorum sensing (QS) system was recognized to be involved in the regulation of a range of functions in diverse bacteria. In contrast to other autoinducers that are specific for a narrow range of organisms, the widely conserved AI-2 has been hypothesized to be a universal language for interspecies communication. In every case, AI-2 is synthesized by LuxS, which functions in the pathway for metabolism of S-adenosylmethionine (SAM), a major cellular methyl donor. In a metabolic pathway known as the activated methyl cycle, SAM is metabolized to Sadenosylhomocysteine, which is subsequently converted to adenine, homocysteine, and 4, 5-dihydroxy-2, 3-pentanedione (DPD, the precursor of AI-2) by the sequential action of the enzymes Pfs and LuxS. DPD is a highly reactive product that can rearrange and undergo additional reactions, suggesting that distinct but related molecules derived from DPD may be the signals that different bacterial species recognize as AI-2. That’s to say, LuxS protein is an important enzyme that can catalyze the conversion of 4, 5-dihydroxy-2, 3-pentanedione (DPD, the precursor of AI-2) to AI2.
In our entire regulatory system, the LuxS gene has been proved to be able to express proteins normally and to assist in generating signaling molecules that initiate the quorum-sensing (Figure 1). Moreover, the LuxS gene can express whether it was lactic acid or not (Figure 2).
As the following figures showed, when lldPRD operon promoter-LuxS worked with LsrA-GFP and lldPRD operon promoter-LuxS-Lldr with LsrA-GFP, the QS system could be activated in the presence of lactic acid, which indicated that the LuxS gene can work properly in the system. (Figure 3, Figure 4)
Figure 1: Characterization of LuxS under different concentrations of lactic acid and IPTG. The LuxS protein had been an obvious protein band between the last two marker bands of 15kDa and 25kDa. The molecular weight of the LuxS protein is about 17kDa. Lane 1, IPTG 0mM, lactic acid 0mM, O-LuxS; Lane 2, IPTG 0. 5mM, lactic acid 0mM, O-LuxS; Lane 3, IPTG 1mM, lactic acid 0mM, O-LuxS; Lane 4, IPTG 0mM, lactic acid 2mM, O-LuxS; Lane 5, IPTG 0. 5mM, lactic acid 2mM, O-LuxS; Lane 6, IPTG 1mM, lactic acid 2mM, O-LuxS; Lane 7, control( IPTG 0mM, lactic acid 0mM); Lane 8, IPTG 0mM, lactic acid 0mM, O-LuxS-lldR; Lane 9, IPTG 0. 5mM, lactic acid 0mM, O-LuxS-lldR; Lane 10, IPTG 1mM, lactic acid 0mM, O-LuxS-lldR; Lane 11, IPTG 0mM, lactic acid 2mM, O-LuxS-lldR; Lane 12, IPTG 0. 5mM, lactic acid 2mM, O-LuxS-lldR; Lane 13, IPTG 1mM, lactic acid 2mM, O-LuxS-lldR.
Figure 2:LuxS with Time
Figure 3: lldPRD operon promoter-LuxS work with LsrA promoter-GFP
Figure 4: lldPRD operon promoter-LuxS-Lldr work with LsrA promoter-GFP
Sequence and Features
- 10COMPATIBLE WITH RFC
- 12COMPATIBLE WITH RFC
- 21Illegal BamHI site found at 155
- 23COMPATIBLE WITH RFC
- 25Illegal AgeI site found at 253
- 1000COMPATIBLE WITH RFC