periplasmic substrate-binding domain of active transport proteins (substrate binding proteins or SBPs)
Periplasmic substrate-binding domain of active transport proteins found in gram-negative and gram-positive bacteria. Members of this group are initial receptors in the process of active transport across cellular membrane, but their substrate specificities are not known in detail. However, they closely resemble the group of AmiC and active transport systems for short-chain amides and urea (FmdDEF), and thus are likely to exhibit a ligand-binding mode similar to that of the amide sensor protein AmiC from Pseudomonas aeruginosa. Moreover, this binding domain has high sequence identity to the family of hydrophobic amino acid transporters (HAAT), and thus it may also be involved in transport of amino acids.
Jiyao W et al.(2023). "The conserved domain database in 2023.",