Protein-protein interaction in transport: periplasmic histidine-binding protein J interacts with P protein.

A component of the high-affinity histidine transport system in Salmonella typhimurium, the periplasmic histidine-binding protein J, interacts with another transport component, the P protein. A mutant J protein, with a defective interaction site but intact histidine-binding site, can function in histidine transport if an appropriate compensating mutation is introduced in the P protein. The interaction between the J and P proteins is an obligatory step in transport. The significance of this interaction and of the involvement of the P protein in multiple transport functions is discussed.