Document Detail

The ion coupling and organic substrate specificities of osmoregulatory transporter ProP in Escherichia coli.
MedLine Citation:
PMID:  10446288     Owner:  NLM     Status:  MEDLINE    
Transporter ProP of Escherichia coli, a member of the major facilitator superfamily, mediates osmoprotective proline or glycine betaine accumulation by bacteria exposed to high osmolality environments. Morpholinopropane sulfonic acid, a common constituent of microbiological media, accumulates in osmoadapting E. coli cells but it is not osmoprotective and it did not influence proP transcription or ProP activity. The apparent K(m) for proline uptake via ProP increased with decreasing pH in the range 7.5-4. ProP-dependent proline uptake by de-energized bacteria was associated with alkalinization of the external medium. Thus ProP mediates cotransport of H(+) and zwitterionic proline and a transporter functional group with a pK(a) of 5-6 is implicated in catalysis. Exogenous proline or glycine betaine elicits K(+) release from osmoadapting E. coli cells and ProP activity is stimulated by exogenous K(+). However, uptake of proline or glycine betaine stimulated K(+) efflux from K(+)-loaded bacteria which expressed either ProP or alternative, osmoregulatory transporter ProU. This indicated that ProP was unlikely to mediate K(+) efflux. Zwitterions ectoine, pipecolate, proline betaine, N,N-dimethylglycine, carnitine and 1-carboxymethylpyridinium were identified as alternative ProP substrates. Choline, a cation and a structural analogue of glycine betaine, was a low affinity inhibitor but not a substrate of ProP.
S V MacMillan; D A Alexander; D E Culham; H J Kunte; E V Marshall; D Rochon; J M Wood
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Biochimica et biophysica acta     Volume:  1420     ISSN:  0006-3002     ISO Abbreviation:  Biochim. Biophys. Acta     Publication Date:  1999 Aug 
Date Detail:
Created Date:  1999-09-28     Completed Date:  1999-09-28     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0217513     Medline TA:  Biochim Biophys Acta     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  30-44     Citation Subset:  IM    
Department of Microbiology, University of Guelph, Guelph, Ont. N1G 2W1, Canada.
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MeSH Terms
Bacterial Proteins / antagonists & inhibitors,  genetics,  metabolism*
Betaine / metabolism
Biological Transport, Active
Carrier Proteins / antagonists & inhibitors,  genetics,  metabolism*
Choline / metabolism,  pharmacology
Escherichia coli / genetics,  metabolism*
Escherichia coli Proteins*
Hydrogen-Ion Concentration
Ion Transport
Potassium / metabolism
Proline / metabolism
Water-Electrolyte Balance
Reg. No./Substance:
0/Bacterial Proteins; 0/Carrier Proteins; 0/Escherichia coli Proteins; 0/ProP protein, E coli; 0/Symporters; 107-43-7/Betaine; 147-85-3/Proline; 62-49-7/Choline; 7440-09-7/Potassium

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

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