Degradation of the E. coli antitoxin MqsA by the proteolytic complex ClpXP is regulated by zinc occupancy and oxidation

Abstract It is well established that the antitoxins of toxin–antitoxin (TA) systems are selectively degraded by bacterial proteases in response to stress. However, how distinct stressors result in the selective degradation of specific antitoxins remain unanswered. MqsRA is a TA system activated by various stresses, including oxidation. Here, we reconstituted the Escherichia coli ClpXP proteolytic machinery in vitro to monitor degradation of MqsRA TA components. We show that the MqsA antitoxin is a ClpXP proteolysis substrate, and that its degradation