A proton nuclear magnetic resonance investigation of histidine-binding protein J of Salmonella typhimurium: a model for transport of L-histidine across cytoplasmic membrane.

Genetic evidence suggests that the high-affinity L-histidine transport in Salmonella typhimurium requires the participation of a periplasmic binding protein (histidine-binding protein J) and two other proteins (P and Q proteins). The histidine-binding protein J binds L-histidine as the first step in the high-affinity active transport of this amino acid across the cytoplasmic membrane. High-resolution proton nuclear magnetic resonance spectroscopy at 600 MHz is used to investigate the conformations of this protein in the absence and presence of substrate.