The membrane-associated lipoprotein Gna1946 from Neisseria meningitidis; the type 2 periplasmic binding protein fold
Gna1946 shares significant structural and sequence homology with the periplasmic substrate-binding domain of ATP-binding cassette (ABC) transporter involved in uptake of methionine (MetQ). The 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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