Substrate binding domain of phosphonate uptake system-like, a member of the type 2 periplasmic-binding fold superfamily.
This family includes alkylphosphonate binding domain PhnD. These domains are found in PhnD-like proteins that are predicted to function as initial receptors in hypophosphite, phosphonate, or phosphate ABC transport in archaea and eubacteria. PhnD is the periplasmic binding component of an ABC-type phosphonate uptake system (PhnCDE) that recognizes and binds phosphonate. PhnD belongs to the PBP2 superfamily of periplasmic binding proteins that differ in size and ligand specificity, but have similar tertiary structures consisting of two globular subdomains connected by a flexible hinge. The PBP2 have been shown to bind their ligand in the cleft between these domains in a manner resembling a Venus flytrap.
Jiyao W et al.(2023). "The conserved domain database in 2023.",