title: Fine tuning the specificity of the periplasmic phosphate transport receptor. Site-directed mutagenesis, ligand binding, and crystallographic studies.
abstract: Phosphorous, primarily in the form of phosphate, is a critical nutrient for the life of a cell. We have previously determined the 1.7-A resolution structure of the phosphate-binding protein, an initial receptor for the high-affinity phosphate active transport system or permease in Escherichia coli (Luecke, H., and Quiocho, F.A. (1990) Nature 347, 402-406). This structure is the first to reveal the key role of hydrogen bonding interactions in conferring the high specificity of the permease, a specificity also shared by other phosphate transport systems. Both monobasic and dibasic phosphates are recognized by the phosphate-binding protein with Asp56 playing a key role. Here we report site-directed mutagenesis, ligand binding, and crystallographic studies of the binding protein which show that introduction of one additional Asp by mutagenesis of the Thr141 in the ligand-binding site restricts binding to only the monobasic phosphate.
authors.affiliation: Structural and Computational Biology and Molecular Biophysics Program, Baylor College of Medicine, Houston, Texas 77030.
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.forename: A
authors.initials: A
authors.lastname: Choudhary
authors.forename: P S
authors.initials: PS
authors.lastname: Ledvina
authors.forename: F A
authors.initials: FA
authors.lastname: Quiocho
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry*; D003461:Crystallography; D004926:Escherichia coli / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D016297:Mutagenesis, Site-Directed; D009169:Mycobacterium tuberculosis / Q000737:chemistry; D028044:Phosphate-Binding Proteins; D010710:Phosphates / Q000378:metabolism*; D012680:Sensitivity and Specificity
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D028044:Phosphate-Binding Proteins; D010710:Phosphates