The C-terminal substrate binding domain of LysR-type transcriptional regulator, IlvR, involved in the biosynthesis of isoleucine, leucine and valine; contains type 2 periplasmic binding fold.
The IlvR is an activator of the upstream and divergently transcribed ilvD gene, which encodes dihydroxy acid dehydratase that participates in isoleucine, leucine, and valine biosynthesis. As in the case of other members of the LysR family, the expression of ilvR gene is repressed in the presence of its own gene product. This substrate-binding domain shows significant homology to the type 2 periplasmic binding proteins (PBP2), which are responsible for the uptake of a variety of substrates such as phosphate, sulfate, polysaccharides, lysine/arginine/ornithine, and histidine. The PBP2 bind their ligand in the cleft between these domains in a manner resembling a Venus flytrap. After binding their specific ligand with high affinity, they can interact with a cognate membrane transport complex comprised of two integral membrane domains and two cytoplasmically located ATPase domains. This interaction triggers the ligand translocation across the cytoplasmic membrane energized by ATP hydrolysis.