PMID:10027982

Citation	Freeman, JA and Bassler, BL (1999) A genetic analysis of the function of LuxO, a two-component response regulator involved in quorum sensing in Vibrio harveyi. Mol. Microbiol. 31:665-77
Abstract	Two independent quorum-sensing systems control the expression of bioluminescence (lux) in the marine bacterium Vibrio harveyi. Each system is composed of an autoinducer (AI-1 or AI-2) and its cognate sensor (LuxN or LuxQ). The sensors are two-component hybrid kinases, containing both sensor kinase domains and response regulator domains. Sensory information from the two systems is relayed by a phosphotransfer mechanism to a shared integrator protein called LuxO. LuxO is a member of the response regulator class of the two-component family of signal transduction proteins, and LuxO acts negatively to control luminescence. In this report, missense and in frame deletion mutations were constructed in luxO that encoded proteins mimicking either the phosphorylated or the unphosphorylated form, and these mutations were introduced into the V. harveyi chromosome at the luxO locus. Phenotypical analyses of the resulting mutant V. harveyi strains indicate that the phosphorylated form of LuxO is the repressor, and that the unphosphorylated form of the protein is inactive. Analysis of the lux phenotypes of V. harveyi strains containing single and double luxN and luxQ mutations indicate that LuxN and LuxQ have two activities on LuxO. They act as LuxO protein kinases at low cell density in the absence of autoinducers, and they switch to LuxO protein phosphatases at high cell density in the presence of autoinducers. Furthermore, the timing and potency of inputs from the two systems into regulation of quorum sensing are different.
Links	PubMed
Keywords	Bacterial Proteins/genetics; Chromosomes, Bacterial; Diploidy; Gene Expression Regulation, Bacterial; Luminescent Measurements; Mutagenesis; Phenotype; Phosphorylation; Phosphotransferases; Protein Kinases/genetics; Repressor Proteins/genetics; Transcription Factors; Vibrio/genetics
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
VIBHB:LUXO		GO:0045892: negative regulation of transcription, DNA-dependent	ECO:0000315:		P		Fig 2 A&B: At high cell densities, LuxO acts as if unphosphorylated, while at low cell densities, LuxO acts as if phosphorylated and represses luminescence	complete CACAO 8781
VIBHB:LUXO		GO:0006355: regulation of transcription, DNA-dependent	ECO:0000315:		P		Fig 2: At high cell densities, LuxO acts as if de-phosphorylated, while at low cell densities, LuxO acts as if phosphorylated and represses luminescence.	complete CACAO 9004
VIBHA:LUXQ	involved_in	GO:0023014: signal transduction by protein phosphorylation	ECO:0000316: genetic interaction evidence used in manual assertion	UniProtKB:A7MRY4	P		Seeded From UniProt	complete
VIBHA:LUXQ		GO:0016310: phosphorylation	ECO:0000315:		P		Figure 5: Lack of LuxN and LuxQ sensors resulted in unphosphorylated LuxO which led to constant luminescence.	complete CACAO 8783
VIBHA:LUXQ		GO:0023014: signal transduction by phosphorylation	ECO:0000316:	UniProtKB:A7MRY4	P		Figure 5: Lack of LuxN and LuxQ sensors resulted in unphosphorylated LuxO which led to constant luminescence.	complete CACAO 9011
VIBHA:LUXO		GO:0000156: phosphorelay response regulator activity	ECO:0000315:		F		Figure 2: LuxO point mutations at Asp-47 resulting in a non-phosphorylated protein mimic causes constitutive luminescence. LuxO point mutations at Asp-47 resulting in a phosphorylated protein mimic causes nearly no light production.	complete CACAO 9657
VIBCB:LUXO		GO:0000156: phosphorelay response regulator activity	ECO:0000315:		F		Figure 2: LuxO point mutations at Asp-47 resulting in a non-phosphorylated protein mimic causes constitutive luminescence. LuxO point mutations at Asp-47 resulting in a phosphorylated protein mimic causes nearly no light production.	complete CACAO 9668
VIBCB:LUXN		GO:0023014: signal transduction by protein phosphorylation	ECO:0000316: genetic interaction evidence used in manual assertion	UniProtKB:P54302	P		Figure 5: Lack of LuxN and LuxQ sensors resulted in unphosphorylated LuxO which led to constant luminescence.	complete CACAO 9009
VIBCB:LUXN	involved_in	GO:0023014: signal transduction by protein phosphorylation	ECO:0000316: genetic interaction evidence used in manual assertion	UniProtKB:P54302	P		Seeded From UniProt	complete

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