The binding activities of proteins that bind Ap4A, an alarmone, are stimulated in the presence of ethanol or phosphatidylethanolamine.

Three proteins binding Ap4A which is known to increase in the heat-shocked cells or to trigger DNA synthesis in G1-arrested eukaryotic cells were purified from E. coli cell extract. For the binding activities of the proteins, glutathione or dithiothreitol and manganese or iron ion were absolutely required. Glutathione, which exists in relatively high concentration in the cells and had been reported to be related to oxidant shock, was far more effective than an artificial antioxidant, dithiothreitol. Ethanol, which has an effect similar to heat or oxidant shock on microbial or eukaryotic cells, enhanced several fold the Ap4A-binding activity. Phosphatidylethanolamine, a major component of phospholipids of cytoplasma and membrane of E. coli cell also stimulated the Ap4A-binding activity.