Determinants of substrate specificity and biochemical properties of the sn-glycerol-3-phosphate ATP binding cassette transporter (UgpB-AEC2) of Escherichia coli

Steven Wuttge, Martin Bommer, Franziska Jager, Berta M. Martins, Sophie Jacob, Anke Licht, Frank Scheffel, Holger Dobbek, Erwin Schneider

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    23 Citations (Scopus)


    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 basedon 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 G3Pwas solved at 1.8Å 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 complex displayed UgpB/G3P-stimulated ATPase activity inproteoliposomes 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.
    Original languageEnglish
    Pages (from-to)908-920
    Number of pages13
    JournalMolecular Microbiology
    Issue number4
    Publication statusPublished - Nov 2012


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