title: A topological model for the general aromatic amino acid permease, AroP, of Escherichia coli.
abstract: The general aromatic amino acid permease, AroP, of Escherichia coli is responsible for the active transport of phenylalanine, tyrosine, and tryptophan. A proposed topological model for the AroP permease, consisting of 12 hydrophobic transmembrane spans connected by hydrophilic loops, is very similar to that of the closely related phenylalanine-specific permease. The validity of this model and its similarity to that of the PheP permease were investigated by studying fusion proteins of AroP permease and alkaline phosphatase. Based on the results obtained from the AroP-alkaline phosphatase sandwich fusions, we have significantly revised the proposed topological model for AroP in two regions. In this modified AroP topological model, the three charged residues E151, E153, and K160 are repositioned within the membrane in span 5. These three residues are conserved in a large family of amino acid transport proteins, and site-directed mutagenesis identifies them as being essential for transport activity. It is postulated that these residues together with E110 in transmembrane span 3 may be involved in a proton relay system.
authors.affiliation: Department of Microbiology, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: A J
authors.initials: AJ
authors.lastname: Cosgriff
authors.forename: A J
authors.initials: AJ
authors.lastname: Pittard
mesh_terms: D000469:Alkaline Phosphatase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D026905:Amino Acid Transport Systems; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D001692:Biological Transport / Q000235:genetics; D002352:Carrier Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D003001:Cloning, Molecular; D004789:Enzyme Activation / Q000235:genetics; D004795:Enzyme Stability / Q000235:genetics; D004926:Escherichia coli / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins; D018698:Glutamic Acid / Q000502:physiology; D008239:Lysine / Q000502:physiology; D026901:Membrane Transport Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed
chemical_list: D026905:Amino Acid Transport Systems; C063201:AroP protein, E coli; D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D018698:Glutamic Acid; D000469:Alkaline Phosphatase; D008239:Lysine