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Determinants of substrate specificity and biochemical properties of the sn-glycerol-3-phosphate ATP binding cassette transporter (UgpB-AEC(2) ) of Escherichia coli.
MedLine Citation:
PMID:  23013274     Owner:  NLM     Status:  Publisher    
Under phosphate starvation conditions, Escherichia coli can utilize sn-glycerol-3-phosphate (G3P) and G3P diesters as phosphate source when transported by an ATP binding cassette importer composed of the periplasmic binding protein, UgpB, the transmembrane subunits, UgpA and UgpE, and a homodimer of the nucleotide binding subunit, UgpC. The current knowledge on the Ugp transporter is solely based on genetic evidence and transport assays using intact cells. Thus, we set out to characterize its properties at the level of purified protein components. UgpB was demonstrated to bind G3P and glycerophosphocholine with dissociation constants of 0.68 ± 0.02 μM and 5.1 ± 0.3 μM, respectively, while glycerol-2-phosphate (G2P) is not a substrate. The crystal structure of UgpB in complex with G3P was solved at 1.8 Å resolution and revealed the interaction with two tryptophan residues as key to the preferential binding of linear G3P in contrast to the branched G2P. Mutational analysis validated the crucial role of Trp-169 for G3P binding. The purified UgpAEC(2) complex displayed UgpB/G3P-stimulated ATPase activity in proteoliposomes that was neither inhibited by phosphate nor by the signal transducing protein PhoU or the phosphodiesterase UgpQ. Furthermore, a hybrid transporter composed of MalFG-UgpC could be functionally reconstituted while a UgpAE-MalK complex was unstable.
Steven Wuttge; Martin Bommer; Franziska Jäger; Berta M Martins; Sophie Jacob; Anke Licht; Frank Scheffel; Holger Dobbek; Erwin Schneider
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-9-27
Journal Detail:
Title:  Molecular microbiology     Volume:  -     ISSN:  1365-2958     ISO Abbreviation:  Mol. Microbiol.     Publication Date:  2012 Sep 
Date Detail:
Created Date:  2012-9-27     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8712028     Medline TA:  Mol Microbiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
© 2012 Blackwell Publishing Ltd.
Division of Microbial Physiology, Humboldt-Universität zu Berlin, Unter den Linden 6, D-10099, Berlin, Germany.
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