The periplasmic-binding component of ABC-type methionine uptake transporter system and its related lipoproteins; the type 2 periplasmic-binding protein fold
This family represents the periplasmic substrate-binding domain of ATP-binding cassette (ABC) transporter involved in uptake of methionine (MetQ) and its related homologs. Members of the MetQ-like family include the 32-kilodalton lipoprotein (Tp32) from Treponema pallidum, the membrane-associated lipoprotein-9 GmpC from Staphylococcus aureus, and Toll-like receptor 2-activating lipoprotein IlpA from Vibrio vulnificus. They all function as a receptor for methionine. This substrate-binding domain belongs to the type 2 periplasmic binding fold protein superfamily (PBP2). The PBP2 proteins are typically 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. The majority of PBP2 proteins function in the uptake of small soluble substrates in eubacteria and archaea.
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