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'''Autoinducer-2''' (AI-2), a furanosyl [[borate ester|borate diester]], is a member of a family of [[signaling molecule]]s used in [[quorum sensing]].<ref>{{Cite journal| last1= Cao | first1= Jie-Gang | last2= Meighen | first2= Edward A. | year= 1989 | title= Purification and structural identification of an autoinducer for the luminescence system of Vibrio harveyi | journal= [[Journal of Biological Chemistry]] | volume= 264 | issue= 36 | pages= 21670–21676 | pmid= 2600086 }}</ref> AI-2 is unique in that it is one of only a few known biomolecules incorporating [[boron]]. First identified in the marine bacterium ''[[Vibrio harveyi]]'', AI-2 is produced and recognized by many [[Gram-negative]] and [[Gram-positive bacteria]].<ref>{{Cite journal| doi= 10.1016/j.molcel.2004.07.020| last1= Miller | first1= Stephen T. | last2= Xavier | first2= Karina B. | last3= Campagna | first3= Shawn R. | last4= Taga | first4= Michiko E. | last5= Semmelhack | first5= Martin F. | last6= Bassler | first6= Bonnie L. | last7= Hughson | first7= Frederick M. | year= 2004 | title= Salmonella typhimurium Recognizes a Chemically Distinct Form of the Bacterial Quorum-Sensing Signal AI-2 | journal= [[Molecular Cell]] | volume= 15 | issue= 5 | pages= 677–687 | pmid= 15350213 }}</ref><ref>{{Cite journal| doi= 10.1146/annurev.micro.55.1.165| last1= Miller | first1= M. B. | last2= Bassler | first2= B. L. | year= 2001 | title= Quorum sensing in bacteria | journal= [[Annual Review of Microbiology]] | volume= 55 | series= | issue= | pages= 165–199 | pmid= 11544353 }}</ref> AI-2 is synthesized by the reaction of 1-deoxy-3-dehydro-D-[[ribulose]] with [[boric acid]].<ref>http://www.chem.qmul.ac.uk/iubmb/enzyme/reaction/misc/AI2.html</ref>
'''Autoinducer-2''' (AI-2), a furanosyl [[borate ester|borate diester]], is a member of a family of [[signaling molecule]]s used in [[quorum sensing]].<ref>{{Cite journal| last1= Cao | first1= Jie-Gang | last2= Meighen | first2= Edward A. | year= 1989 | title= Purification and structural identification of an autoinducer for the luminescence system of Vibrio harveyi | journal= [[Journal of Biological Chemistry]] | volume= 264 | issue= 36 | pages= 21670–21676 | pmid= 2600086 }}</ref> AI-2 is unique in that it is one of only a few known [[biomolecules]] incorporating [[boron]]. First identified in the marine bacterium ''[[Vibrio harveyi]]'', AI-2 is produced and recognized by many [[Gram-negative]] and [[Gram-positive bacteria]].<ref>{{Cite journal| doi= 10.1016/j.molcel.2004.07.020| last1= Miller | first1= Stephen T. | last2= Xavier | first2= Karina B. | last3= Campagna | first3= Shawn R. | last4= Taga | first4= Michiko E. | last5= Semmelhack | first5= Martin F. | last6= Bassler | first6= Bonnie L. | last7= Hughson | first7= Frederick M. | year= 2004 | title= Salmonella typhimurium Recognizes a Chemically Distinct Form of the Bacterial Quorum-Sensing Signal AI-2 | journal= [[Molecular Cell]] | volume= 15 | issue= 5 | pages= 677–687 | pmid= 15350213 }}</ref><ref>{{Cite journal| doi= 10.1146/annurev.micro.55.1.165| last1= Miller | first1= M. B. | last2= Bassler | first2= B. L. | year= 2001 | title= Quorum sensing in bacteria | journal= [[Annual Review of Microbiology]] | volume= 55 | series= | issue= | pages= 165–199 | pmid= 11544353 }}</ref> AI-2 is synthesized by the reaction of 1-deoxy-3-dehydro-D-[[ribulose]] with [[boric acid]].<ref>http://www.chem.qmul.ac.uk/iubmb/enzyme/reaction/misc/AI2.html</ref>


AI-2 is sensed by the Lsr transport cassette and is actively transported into the cell,{{clarify|date=October 2010}}<!-- which/how many species has this been demonstrated in?--> where it is phosphorylated by {{SWL|target=LsrK|type=phosphorylated_by}}. Then, Phospho-AI-2 binds the transcriptional repressor protein, LsrR, which subsequently is released from the promoter/operator region of the lsr operon – and transcription of the lsr genes is initiated. AI-2 signalling is also regulated by glucose and cAMP/CRP via the lsr operon. In the presence of glucose, low levels of cAMP/CRP result in almost no lsr operon (lsrABCDFG) expression. Without glucose, cAMP-CRP is needed to stimulate the lsr expression, while LsrR represses its expression in the absence of the inducer, phospho-AI-2. As AI-2 accumulates, more AI-2 is taken in via LsrABCD, phosphorylated via LsrK, and the lsr transcription is de-repressed, enabling even more AI-2 uptake.<ref>{{Cite journal| doi= 10.1128/JB.187.6.2066-2076.2005| last1= Wang | first1= Liang | last2= Hashimoto | first2= Yoshifumi | last3= Tsao | first3= Chen-Yu | last4= Valdes | first4= James J. | last5= Bentley | first5= William E. | year= 2005 | title= Cyclic AMP (cAMP) and cAMP Receptor Protein Influence both Synthesis and Uptake of Extracellular Autoinducer 2 in Escherichia coli | journal= [[Journal of Bacteriology]] | volume= 187 | issue= 6 | pages= 2066–2076 | pmid= 15743955| pmc= 1064054 }}</ref>
AI-2 is sensed by the Lsr transport cassette and is actively transported into the cell,{{clarify|date=October 2010}}<!-- which/how many species has this been demonstrated in?--> where it is phosphorylated by {{SWL|target=LsrK|type=phosphorylated_by}}. Then, Phospho-AI-2 binds the transcriptional repressor protein, LsrR, which subsequently is released from the promoter/operator region of the lsr operon – and transcription of the lsr genes is initiated. AI-2 signalling is also regulated by glucose and cAMP/CRP via the lsr operon. In the presence of glucose, low levels of cAMP/CRP result in almost no lsr operon (lsrABCDFG) expression. Without glucose, cAMP-CRP is needed to stimulate the lsr expression, while LsrR represses its expression in the absence of the inducer, phospho-AI-2. As AI-2 accumulates, more AI-2 is taken in via LsrABCD, phosphorylated via LsrK, and the lsr transcription is de-repressed, enabling even more AI-2 uptake.<ref>{{Cite journal| doi= 10.1128/JB.187.6.2066-2076.2005| last1= Wang | first1= Liang | last2= Hashimoto | first2= Yoshifumi | last3= Tsao | first3= Chen-Yu | last4= Valdes | first4= James J. | last5= Bentley | first5= William E. | year= 2005 | title= Cyclic AMP (cAMP) and cAMP Receptor Protein Influence both Synthesis and Uptake of Extracellular Autoinducer 2 in Escherichia coli | journal= [[Journal of Bacteriology]] | volume= 187 | issue= 6 | pages= 2066–2076 | pmid= 15743955| pmc= 1064054 }}</ref>

Revision as of 21:02, 4 August 2012

Autoinducer-2
Autoinducer-2
Names
IUPAC name
(3aS,6S,6aR)-2,2,6,6a-tetrahydroxy-3a-methyltetrahydrofuro[3,2-d][1,3,2]dioxaborolan-2-uide)
Other names
Dihydroxy[(2S,3R,4S)-2-methyldihydro-
Identifiers
3D model (JSmol)
ChemSpider
  • InChI=1S/C5H10BO7/c1-4-5(8,3(7)2-11-4)13-6(9,10)12-4/h3,7-10H,2H2,1H3/q-1/t3-,4+,5+/m0/s1
    Key: ACKRRKSNOOISSG-VPENINKCSA-N
  • InChI=1/C5H10BO7/c1-4-5(8,3(7)2-11-4)13-6(9,10)12-4/h3,7-10H,2H2,1H3/q-1/t3-,4+,5+/m0/s1
    Key: ACKRRKSNOOISSG-VPENINKCBL
  • O[C@@H]1[C@]2(O[B-](O[C@]2(OC1)C)(O)O)O
Properties
C5H10BO7
Molar mass 192.940
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Autoinducer-2 (AI-2), a furanosyl borate diester, is a member of a family of signaling molecules used in quorum sensing.[1] AI-2 is unique in that it is one of only a few known biomolecules incorporating boron. First identified in the marine bacterium Vibrio harveyi, AI-2 is produced and recognized by many Gram-negative and Gram-positive bacteria.[2][3] AI-2 is synthesized by the reaction of 1-deoxy-3-dehydro-D-ribulose with boric acid.[4]

AI-2 is sensed by the Lsr transport cassette and is actively transported into the cell,[clarification needed] where it is phosphorylated by Template:SWL. Then, Phospho-AI-2 binds the transcriptional repressor protein, LsrR, which subsequently is released from the promoter/operator region of the lsr operon – and transcription of the lsr genes is initiated. AI-2 signalling is also regulated by glucose and cAMP/CRP via the lsr operon. In the presence of glucose, low levels of cAMP/CRP result in almost no lsr operon (lsrABCDFG) expression. Without glucose, cAMP-CRP is needed to stimulate the lsr expression, while LsrR represses its expression in the absence of the inducer, phospho-AI-2. As AI-2 accumulates, more AI-2 is taken in via LsrABCD, phosphorylated via LsrK, and the lsr transcription is de-repressed, enabling even more AI-2 uptake.[5]

Doubts have been expressed regarding AI-2's status as a universal signal. The gene responsible for its production is the widespread luxS; this gene has an important role in the recycling of S-adenosyl-L-methionine, with AI-2 being a metabolic by-product of that process.[6] While it is certainly true that some bacteria respond to AI-2, it is not yet clear that it is always being produced for purposes of signalling.

References

  1. ^ Cao, Jie-Gang; Meighen, Edward A. (1989). "Purification and structural identification of an autoinducer for the luminescence system of Vibrio harveyi". Journal of Biological Chemistry. 264 (36): 21670–21676. PMID 2600086.
  2. ^ Miller, Stephen T.; Xavier, Karina B.; Campagna, Shawn R.; Taga, Michiko E.; Semmelhack, Martin F.; Bassler, Bonnie L.; Hughson, Frederick M. (2004). "Salmonella typhimurium Recognizes a Chemically Distinct Form of the Bacterial Quorum-Sensing Signal AI-2". Molecular Cell. 15 (5): 677–687. doi:10.1016/j.molcel.2004.07.020. PMID 15350213.
  3. ^ Miller, M. B.; Bassler, B. L. (2001). "Quorum sensing in bacteria". Annual Review of Microbiology. 55: 165–199. doi:10.1146/annurev.micro.55.1.165. PMID 11544353.
  4. ^ http://www.chem.qmul.ac.uk/iubmb/enzyme/reaction/misc/AI2.html
  5. ^ Wang, Liang; Hashimoto, Yoshifumi; Tsao, Chen-Yu; Valdes, James J.; Bentley, William E. (2005). "Cyclic AMP (cAMP) and cAMP Receptor Protein Influence both Synthesis and Uptake of Extracellular Autoinducer 2 in Escherichia coli". Journal of Bacteriology. 187 (6): 2066–2076. doi:10.1128/JB.187.6.2066-2076.2005. PMC 1064054. PMID 15743955.
  6. ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1098/rstb.2007.2049, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1098/rstb.2007.2049 instead.
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