Document Detail

Isovaleryl-homoserine lactone, an unusual branched-chain quorum-sensing signal from the soybean symbiont Bradyrhizobium japonicum.
MedLine Citation:
PMID:  21949379     Owner:  NLM     Status:  MEDLINE    
Many species of Proteobacteria communicate by using LuxI-LuxR-type quorum-sensing systems that produce and detect acyl-homoserine lactone (acyl-HSL) signals. Most of the known signals are straight-chain fatty acyl-HSLs, and evidence indicates that LuxI homologs prefer fatty acid-acyl carrier protein (ACP) over fatty acyl-CoA as the acyl substrate for signal synthesis. Two related LuxI homologs, RpaI and BtaI from Rhodopseudomonas palustris and photosynthetic stem-nodulating bradyrhizobia, direct production of the aryl-HSLs p-coumaroyl-HSL and cinnamoyl-HSL, respectively. Here we report that BjaI from the soybean symbiont Bradyrhizobium japonicum USDA110 is closely related to RpaI and BtaI and catalyzes the synthesis of isovaleryl-HSL (IV-HSL), a branched-chain fatty acyl-HSL. We show that IV-HSL induces expression of bjaI, and in this way IV-HSL functions like many other acyl-HSL quorum-sensing signals. Purified histidine-tagged BjaI was an IV-HSL synthase, which was active with isovaleryl-CoA but not detectably so with isovaleryl-ACP. This suggests that the RpaI-BtaI-BjaI subfamily of acyl-HSL synthases may use CoA- rather than ACP-linked substrates for acyl-HSL synthesis. The bjaI-linked bjaR(1) gene is involved in the response to IV-HSL, and BjaR(1) is sensitive to IV-HSL at concentrations as low as 10 pM. Low but sufficient levels of IV-HSL (about 5 nM) accumulate in B. japonicum culture fluid. The low levels of IV-HSL synthesis have likely contributed to the fact that the quorum-sensing signal from this bacterium has not been described elsewhere.
Andrea Lindemann; Gabriella Pessi; Amy L Schaefer; Margrith E Mattmann; Quin H Christensen; Aline Kessler; Hauke Hennecke; Helen E Blackwell; E Peter Greenberg; Caroline S Harwood
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2011-09-26
Journal Detail:
Title:  Proceedings of the National Academy of Sciences of the United States of America     Volume:  108     ISSN:  1091-6490     ISO Abbreviation:  Proc. Natl. Acad. Sci. U.S.A.     Publication Date:  2011 Oct 
Date Detail:
Created Date:  2011-10-05     Completed Date:  2011-12-13     Revised Date:  2013-06-27    
Medline Journal Info:
Nlm Unique ID:  7505876     Medline TA:  Proc Natl Acad Sci U S A     Country:  United States    
Other Details:
Languages:  eng     Pagination:  16765-70     Citation Subset:  IM    
Department of Microbiology, University of Washington, Seattle, WA 98195, USA.
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MeSH Terms
4-Butyrolactone / analogs & derivatives*,  metabolism
Acyl Coenzyme A / metabolism
Amino Acid Sequence
Bacterial Proteins / genetics,  metabolism
Bradyrhizobium / metabolism*,  physiology
Cluster Analysis
Computational Biology
Gene Expression Regulation, Bacterial / physiology*
Quorum Sensing / physiology*
Reverse Transcriptase Polymerase Chain Reaction
Sequence Alignment
Soybeans / microbiology*
Transcription Factors / genetics,  metabolism
Grant Support
Reg. No./Substance:
0/Acyl Coenzyme A; 0/Bacterial Proteins; 0/LuxI protein, Bacteria; 0/Transcription Factors; 1192-20-7/homoserine lactone; 6244-91-3/isovaleryl-coenzyme A; 96-48-0/4-Butyrolactone

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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