The C-terminal substrate binding domain of LysR-type transcriptional regulators, YofA and SoxR, contains the type 2 periplasmic binding fold.
YofA is a LysR-like transcriptional regulator of cell growth in Bacillus subtillis. YofA controls cell viability and the formation of constrictions during cell division. YofaA positively regulates expression of the cell division gene ftsW, and thus is essential for cell viability during stationary-phase growth of Bacillus substilis. YofA shows significant homology to SoxR from Arthrobacter sp. TE1826. SoxR is a negative regulator for the sarcosine oxidase gene soxA. Sarcosine oxidase catalyzes the oxidative demethylation of sarcosine, which is involved in the metabolism of creatine and choline. The topology of this substrate-binding domain is most similar to that of 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.