Beyond allostery: Catalytic regulation of a deoxyribozyme through an entropy-driven DNA amplifier

The programmability and replicability of RNA and DNA have respectively enabled the design and selection of a number of allosteric ribozymes and deoxyribozymes. These catalysts have been adapted to function as signal transducers in biosensors and biochemical reaction networks both in vitro and in vivo. However, allosteric control of nucleic acid catalysts is currently limited by the fact that one molecule of effector (input) generally regulates at most one molecule of ribozyme or deoxyribozyme (output). In consequence, allosteric control is usually inefficient when the concentration of input molecules is low. In contrast, catalytic regulation of protein enzymes, as in protein phosphorylation cascades, generally allows one input molecule (e.g., one kinase molecule) to regulate multiple output molecules (e.g., kinase substrates). Achieving such catalytic signal amplification would also be of great utility for nucleic acid circuits. Here we show that allosteric regulation of nucleic acid enzymes can be coupled to signal amplification in an entropy-driven DNA circuit. In this circuit, kinetically trapped DNA logic gates are triggered by a specific sequence, and upon execution generate a peroxidase deoxyribozyme that converts a colorless substrate (ABTS) into a green product (ABTS•+). This scheme provides a new paradigm for the design of enzyme-free biosensors for point-of-care diagnostics.