ATP-binding protein that negatively regulates activity of the tripartite ATP-independent periplasmic (TRAP) ectoine transport system TeaABC. May regulate uptake according to the ATP status of the cell. Homodimer or homotetramer; in equilibrium. The dimer/tetramer ratio is ATP-dependent. ATP stabilizes dimer-dimer complexes, with one ATP molecule bound to each monomer. Cotranscribed along with teaABC. Deletion results in an enhanced uptake for ectoine by TeaABC. Belongs to the universal stress protein A family.