TThe periplasmic substrate-binding component of an uncharacterized active transport system closely related to spermidine and putrescine transporters; contains the type 2 periplasmic binding fold.
This family represents the periplasmic substrate-binding domain that functions as the primary high-affinity receptors of ABC-type polyamine transport systems. Polyamine transport plays an essential role in the regulation of intracellular polyamine levels which are known to be elevated in rapidly proliferating cells and tumors. Natural polyamines are putrescine, spermindine, and spermine. They are polycations that play multiple roles in cell growth, survival and proliferation, and plant stress and disease resistance. They can interact with negatively charged molecules, such as nucleic acids, to modulate their functions. Members of this family belong to the type 2 periplasmic-binding fold superfamily. PBP2 is comprised of two globular subdomains connected by a flexible hinge and bind their ligand in the cleft between these domains in a manner resembling a Venus flytrap.
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