A new subfamily of bacterial glutamate/aspartate receptors.
The specificity of bacterial nutrient importers of the ATP-binding cassette (ABC) type depends on external receptor proteins that not only bind the solute to be transported, but also initiate the transport process by inducing ATP hydrolysis in the cytoplasmic nucleotide-binding domains. Here we propose a mode of ligand binding to the solute-binding protein AatJ that is required for glutamate uptake by the AatJMQP transporter in Pseudomonas putida KT2440. A homology model of the AatJ-glutamate complex was constructed using the E. coli glutamine-binding protein GlnH as the template. The general validity of the model was then confirmed by alanine scanning mutagenesis of several residues predicted to interact with the ligand and by semi-quantitative binding studies with [(14)C]-Glu and [(14)C]-Asp. A database search indicated that AatJ is a member of a distinct subfamily of the family 3 solute-binding proteins with specificity towards glutamate and aspartate.
Singh
Birendra
B
Institute of Physiological Chemistry, Philipps University, Karl-von-Frisch-Strasse 1, D-35033 Marburg, Germany. singh@staff.uni-marburg.de
Röhm
Klaus-Heinrich
KH
D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000595:Amino Acid Sequence; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016958:Pseudomonas putida / Q000235:genetics / Q000378:metabolism*; D017459:Receptors, Amino Acid / Q000235:genetics / Q000378:metabolism*; D017470:Receptors, Glutamate / Q000235:genetics / Q000378:metabolism*
D018528:ATP-Binding Cassette Transporters; D017459:Receptors, Amino Acid; D017470:Receptors, Glutamate; C031959:aspartic acid receptor