Importance of the E. coli DinJ antitoxin carboxy terminus for toxin suppression and regulated proteolysis.
Toxin-antitoxin genes play important roles in the regulation of bacterial growth during stress. One response to stress is selective proteolysis of antitoxin proteins which releases their cognate toxin partners causing rapid inhibition of growth. The features of toxin-antitoxin complexes that are important to inhibit toxin activity as well as to release the active toxin remain elusive. Furthermore, it is unclear how antitoxins are selected for proteolysis by cellular proteases. Here, we test the minimal structural requirements of the Escherichia coli DinJ antitoxin to suppress its toxin partner, YafQ. We find that DinJ-YafQ complex formation is critically dependent on the last ten C-terminal residues of DinJ. However, deletion of these 10 DinJ residues has little effect on transcriptional autorepression suggesting that the YafQ toxin is not a critical component of the repression complex in contrast to other toxin-antitoxin systems. We further demonstrate that loop 5 preceding these ten C-terminal residues is important for Lon-mediated proteolysis. These results provide important insights into the critical interactions between toxin-antitoxin pairs necessary to inhibit toxin activity and the regulated proteolysis of antitoxins.
Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Road NE, Atlanta, GA, 30322, USA.
Ajchareeya
A
Ruangprasert
Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Road NE, Atlanta, GA, 30322, USA.
Tatsuya
T
Maehigashi
Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Road NE, Atlanta, GA, 30322, USA.
Stacey J
SJ
Miles
Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Road NE, Atlanta, GA, 30322, USA.
Christine M
0000-0002-8821-688X
CM
Dunham
D000992:Antitoxins / Q000235:genetics; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism*; D000072417:Protein Domains; D017434:Protein Structure, Tertiary; D059748:Proteolysis; D013312:Stress, Physiological
D000992:Antitoxins; D001427:Bacterial Toxins; C523349:DinJ protein, E coli; D029968:Escherichia coli Proteins; C523350:YafQ protein, E coli