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.