Document Detail

Substrate specificity of the citrate transporter CitP of Lactococcus lactis.
MedLine Citation:
PMID:  22563050     Owner:  NLM     Status:  MEDLINE    
The citrate transporter CitP of lactic acid bacteria catalyzes electrogenic precursor-product exchange of citrate versus L-lactate during citrate-glucose cometabolism. In the absence of sugar, L-lactate is replaced by the metabolic intermediates/end products pyruvate, α-acetolactate, and acetate. In this study, the binding and translocation properties of CitP were analyzed systematically for a wide variety of mono- and dicarboxylates of the form X-CR(2)-COO(-), where X represents OH (2-hydroxy acid), O (2-keto acid), or H (acid) and R groups differ in size, hydrophobicity, and composition. It follows that CitP is a very promiscuous carboxylate transporter. A carboxylate group is both essential and sufficient for recognition by the transporter. A C-2 atom is not essential, formate is a substrate, and C-2 may be part of a ring structure, as in benzoate. The R group may be as bulky as an indole ring structure. For all monocarboxylates of the form X-CHR-COO(-), the hydroxy (X = OH) analogs were the preferred substrates. The preference for keto (X = O) or acid (X = H) analogs was dependent on the bulkiness of the R group, such that the acid was preferred for small R groups and the 2-ketoacid was preferred for more bulky R groups. The C(4) to C(6) dicarboxylates succinate, glutarate, and adipate were also substrates of CitP. The broad substrate specificity is discussed in the context of a model of the binding site of CitP. Many of the substrates of CitP are intermediates or products of amino acid metabolism, suggesting that CitP may have a broader physiological function than its role in citrate fermentation alone.
Agata M Pudlik; Juke S Lolkema
Publication Detail:
Type:  Journal Article     Date:  2012-05-04
Journal Detail:
Title:  Journal of bacteriology     Volume:  194     ISSN:  1098-5530     ISO Abbreviation:  J. Bacteriol.     Publication Date:  2012 Jul 
Date Detail:
Created Date:  2012-06-28     Completed Date:  2012-09-13     Revised Date:  2013-06-25    
Medline Journal Info:
Nlm Unique ID:  2985120R     Medline TA:  J Bacteriol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  3627-35     Citation Subset:  IM    
Top Institute Food and Nutrition, Wageningen, The Netherlands.
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MeSH Terms
Bacterial Proteins / genetics,  metabolism*
Biological Transport, Active
Carboxylic Acids / metabolism*
Gene Expression Regulation, Bacterial / physiology
Hydrogen-Ion Concentration
Lactococcus lactis / genetics,  metabolism*
Organic Anion Transporters / genetics,  metabolism*
Substrate Specificity
Time Factors
Reg. No./Substance:
0/Bacterial Proteins; 0/Carboxylic Acids; 0/Organic Anion Transporters; 77000-09-0/citP protein, Lactococcus lactis

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

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