The C-terminal substrate-domain of LysR-type transcriptional regulators for beta-lactamase genes, contains the type 2 periplasmic binding fold.
This CD includes the C-terminal substrate binding domain of LysR-type transcriptional regulators, BlaA and AmpR, that are involved in control of the expression of beta-lactamase genes. Beta-lactamases are responsible for bacterial resistance to beta-lactam antibiotics such as penicillins. BlaA (a constitutive class A penicillinase) belongs to the LysR family of transcriptional regulators, while BlaB (an inducible class C cephalosporinase or AmpC) can be referred to as a penicillin-binding protein, but it does not act as a beta-lactamase. AmpR regulates the expression of beta-lactamases in many enterobacterial strains and many other gram-negative bacilli. In contrast to BlaA, AmpR acts an activator only in the presence of the beta-lactam inducer. In the absence of the inducer, AmpR acts as a repressor. 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.
Jiyao W et al.(2023). "The conserved domain database in 2023.",