(p)ppGpp Binding to the Bifunctional Enzyme RelSeq Increases Its Conformational Stability

Under adverse environmental conditions bacterial cells survive by activating the “stringent response,” which is mediated by the accumulation of small signaling alarmone molecules (p)ppGpp. The synthesis of (p)ppGpp from ATP and GDP/GTP and their hydrolysis to GDP/GTP and pyrophosphate are catalyzed by enzymes of the RSH (RelA/SpoT Homologue) family. Studying the complex allosteric mechanism underlying the bifunctional activity of these enzymes and the maintenance of intracellular levels of (p)ppGpp is a topical issue in modern science. In this work we determine the conformational stability and binding efficiency of the bifunctional homologue of the RSH family RelSeq385 with nucleotides depending on their concentration and the ionic composition of the reaction mixture.