Document Detail

Halotolerant cyanobacterium Aphanothece halophytica contains a betaine transporter active at alkaline pH and high salinity.
MedLine Citation:
PMID:  16957224     Owner:  NLM     Status:  MEDLINE    
Aphanothece halophytica is a halotolerant alkaliphilic cyanobacterium which can grow in media of up to 3.0 M NaCl and pH 11. This cyanobacterium can synthesize betaine from glycine by three-step methylation using S-adenosylmethionine as a methyl donor. To unveil the mechanism of betaine uptake and efflux in this alkaliphile, we isolated and characterized a betaine transporter. A gene encoding a protein (BetT(A. halophytica)) that belongs to the betaine-choline-carnitine transporter (BCCT) family was isolated. Although the predicted isoelectric pH of a typical BCCT family transporter, OpuD of Bacillus subtilis, is basic, 9.54, that of BetT(A. halophytica) is acidic, 4.58. BetT(A. halophytica) specifically catalyzed the transport of betaine. Choline, gamma-aminobutyric acid, betaine aldehyde, sarcosine, dimethylglycine, and amino acids such as proline did not compete for the uptake of betaine by BetT(A. halophytica). Sodium markedly enhanced betaine uptake rates, whereas potassium and other cations showed no effect, suggesting that BetT(A. halophytica) is a Na(+)-betaine symporter. Betaine uptake activities of BetT(A. halophytica) were high at alkaline pH values, with the optimum pH around 9.0. Freshwater Synechococcus cells overexpressing BetT(A. halophytica) showed NaCl-activated betaine uptake activities with enhanced salt tolerance, allowing growth in seawater supplemented with betaine. Kinetic properties of betaine uptake in Synechococcus cells overexpressing BetT(A. halophytica) were similar to those in A. halophytica cells. These findings indicate that A. halophytica contains a Na(+)-betaine symporter that contributes to the salt stress tolerance at alkaline pH. BetT(A. halophytica) is the first identified transporter for compatible solutes in cyanobacteria.
Surasak Laloknam; Kimihiro Tanaka; Teerapong Buaboocha; Rungaroon Waditee; Aran Incharoensakdi; Takashi Hibino; Yoshito Tanaka; Teruhiro Takabe
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Applied and environmental microbiology     Volume:  72     ISSN:  0099-2240     ISO Abbreviation:  Appl. Environ. Microbiol.     Publication Date:  2006 Sep 
Date Detail:
Created Date:  2006-09-07     Completed Date:  2006-11-08     Revised Date:  2010-09-16    
Medline Journal Info:
Nlm Unique ID:  7605801     Medline TA:  Appl Environ Microbiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  6018-26     Citation Subset:  IM    
Research Institute of Meijo University, Tenpaku-ku, Nagoya 468-8502, Japan.
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MeSH Terms
Bacterial Proteins / genetics,  metabolism*
Base Sequence
Betaine / metabolism
Binding, Competitive
Carrier Proteins / genetics,  metabolism*
Cloning, Molecular
Cyanobacteria / genetics,  metabolism*
DNA, Bacterial / genetics
Escherichia coli / genetics,  growth & development,  metabolism
Genes, Bacterial
Genetic Complementation Test
Hydrogen-Ion Concentration
Molecular Sequence Data
Recombinant Proteins / genetics,  metabolism
Sodium / metabolism
Sodium Chloride / metabolism
Synechococcus / genetics,  metabolism
Transformation, Genetic
Reg. No./Substance:
0/Bacterial Proteins; 0/Carrier Proteins; 0/DNA, Bacterial; 0/Recombinant Proteins; 107-43-7/Betaine; 146313-33-9/betaine plasma membrane transport proteins; 7440-23-5/Sodium; 7647-14-5/Sodium Chloride

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

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