Probable toxic component of a putative type VII toxin-antitoxin (TA) system, probably an RNase. Probably neutralized by cognate antitoxin MJ1379. Neutralization may be due to AMPylation by antitoxin MJ1379. Homodimer, probably forms a complex with cognate antitoxin MJ1379. Modified by cognate antitoxin MJ1379; probably at least 2 successive AMPylation events occur on Tyr-83. Belongs to the HepT RNase toxin family.