Autoinducers are signal molecules involved in quorum sensing, the process of chemical communication that bacteria use to assess cell population density and synchronize behaviour. The molecule (S)-4,5-dihydroxy-2,3-pentanedione (DPD) is produced by many different species of bacteria and is the precursor of the signal molecule autoinducer-2 (AI-2).A variety of bacterial species have the ability to sequester and process the AI-2 present in their environment, thereby interfering with the cell-cell communication of other bacteria. This process involves the lsr operon, induced by AI-2. This operon consists of a transport system that facilitates uptake of the signal, a kinase that phosphorylates the signal to phospho-DPD (P-DPD), and enzymes that are responsible for processing the phosphorylated signal, thereby terminating induction of the lsr operon [].One of the enzymes responsible for processing the phosphorylated signal is LsrF. LsrF catalyzes the transfer of an acetyl moiety from 3-hydroxy-5-phosphonooxypentane-2,4-dione to CoA to form glycerone phosphate and acetyl-CoA [].
Autoinducers are signal molecules involved in quorum sensing, the process of chemical communication that bacteria use to assess cell population density and synchronize behaviour. The molecule (S)-4,5-dihydroxy-2,3-pentanedione (DPD) is produced by many different species of bacteria and is the precursor of the signal molecule autoinducer-2 (AI-2).A variety of bacterial species have the ability to sequester and process the AI-2 present in their environment, thereby interfering with the cell-cell communication of other bacteria. This process involves the lsr operon, induced by AI-2. This operon consists of a transport system that facilitates uptake of the signal, a kinase that phosphorylates the signal to phospho-DPD (P-DPD), and enzymes that are responsible for processing the phosphorylated signal, thereby terminating induction of the lsr operon [].LsrG catalyzes the conversion of (4S)-4-hydroxy-5-phosphonooxypentane-2,3-dione (P-DPD) to 3-hydroxy-5-phosphonooxypentane-2,4-dione (P-HPD) [].
LsrA is part of the ABC transporter complex LsrABCD that imports autoinducer 2 (AI-2), a protein that functions in interspecies cell-cell communication in bacteria. LsrA is responsible for energy coupling to the transport system [].AI-2 is synthesised via theenzyme LuxS and can induce transcription of the Lsr (LuxS regulated) operon (lsrACDBFGE) [, ]. The first four genes of the operon, lsrACDB, encode components of the ATP-binding cassette transporter, whereas the remaining two are required for the modification of AI-2 following internalisation [].
Autoinducers are signal molecules involved in quorum sensing, the process of chemical communication that bacteria use to assess cell population density and synchronize behaviour. The molecule (S)-4,5-dihydroxy-2,3-pentanedione (DPD) is produced by many different species of bacteria and is the precursor of the signal molecule autoinducer-2 (AI-2).A variety of bacterial species have the ability to sequester and process the AI-2 present in their environment, thereby interfering with the cell-cell communication of other bacteria. This process involves the lsr operon, induced by AI-2. This operon consists of a transport system that facilitates uptake of the signal, a kinase that phosphorylates the signal to phospho-DPD (P-DPD), and enzymes that are responsible for processing the phosphorylated signal, thereby terminating induction of the lsr operon [].Autoinducer-2 kinase (also known as LsrK) phosphorylates AI-2. Phosphorylation serves to trap and activate AI-2 within the cell []. Phosphorylated AI-2 (phospho-DPD) binds and inactivates the transcriptional repressor protein LsrR thereby inducing the expression of the lsr operon and potentially other LsrR-regulated, quorum sensing-related genes [, ].
The large serine recombinases (LSRs) are DNA-rearranging enzymes that are members of the serine recombinase or resolvase/invertase superfamily. Most resolvases/invertases have a catalytic domain of ~150 residues at their amino terminus, followed by a small, helix-turn-helix (HTH) DNA-binding domain. The LSRs share a similar amino-terminal catalytic domain, but have much larger carboxyl-terminal regions that range in size from ~300 residues to ~550 residues. The C-terminal region of the LSRs is comprised of multiple structural domains and is responsible for coordination of unique LSRs activities. The LSR C-terminal region is composed of two structural domains: a mixed alpha/beta DNA-binding "recombinase domain"linked to an unusual DNA-binding zinc ribbon domain [, ].The DNA-binding recombinase domain is moderately well conserved among the LSRs and consists of a four stranded β-sheet embedded in a core 4-helix bundle [, ].
The large serine recombinases (LSRs) are DNA-rearranging enzymes that are members of the serine recombinase or resolvase/invertase superfamily. Most resolvases/invertases have a catalytic domain of ~150 residues at their amino terminus, followed by a small, helix-turn-helix (HTH) DNA-binding domain. The LSRs share a similar amino-terminal catalytic domain, but have much larger carboxyl-terminal regions that range in size from ~300 residues to ~550 residues. The C-terminal region of the LSRs is comprised of multiple structural domains and is responsible for coordination of unique LSRs activities. The LSR C-terminal region is composed of two structural domains: a mixed alpha/beta DNA-binding "recombinase domain"linked to an unusual DNA-binding zinc ribbon domain [, ].The DNA-binding recombinase domain is moderately well conserved among the LSRs and consists of a four stranded β-sheet embedded in a core 4-helix bundle [, ].
