Thiaminase-I has high structural homology to the type 2 periplasmic binding proteins of active transport systems
Thiaminase-I, a thiamin-(vitamin B1) degrading enzyme, is a monomer in its biologically active form, with two distinct globular domains (N- and C-domains) separated by a deep groove. It has a structural topology similar to the periplasmic substrate-domains of ABC-type transport systems, such as thiamin-binding protein (TbpA), that possess the type 2 periplasmic binding protein fold. 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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