Conformational dynamics of two histidine-binding proteins of Salmonella typhimurium.
The Salmonella typhimurium periplasmic histidine-binding J-protein is one of four proteins encoded by the histidine transport operon. Mutant J-protein hisJ5625 binds L-histidine, but does not transport it. The tertiary structure and conformational dynamics of native and mutant J-protein have been compared using steady state fluorescence, fluorescence polarization, and fluorescence energy transfer measurements. The two proteins have different three-dimensional structures and exhibit different responses to histidine binding. Ligand-induced conformational changes were demonstrated in both J-proteins using fluorescence energy transfer (distant reporter method) between the single tryptophan residue per mole of protein and a fluorescein-labeled methionine residue. However, the conformational change of the mutant protein is qualitatively and quantitatively different from that of the wild-type protein. Moreover, the microenvironment of the tryptophan and its distance from the labeled methionine (44A for the wild type, 60A for the mutant J-protein) are different in the two proteins. In conclusion, these results indicate that the specific conformational change induced in the wild type J-protein is a necessary requirement for the transport of L-histidine.
D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D006639:Histidine / Q000378:metabolism*; D009154:Mutation; D033902:Periplasmic Binding Proteins; D011487:Protein Conformation; D012486:Salmonella typhimurium / Q000235:genetics / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
D002352:Carrier Proteins; D033902:Periplasmic Binding Proteins; C018963:histidine-binding protein; D006639:Histidine