Probable toxic component of a type VII toxin-antitoxin (TA) system, probably an RNase. Neutralized by cognate antitoxin MntA. Neutralization is probably due to AMPylation by MntA (Probable). A mixture of HepT and MntA binds nucleotides; the highest affinity is for TTP, ATP binds more tightly than ADP or AMP (PubMed:16028221). Homodimer. Forms a complex with MntA, probably with a stoichiometry of 2:2. Modified by cognate antitoxin MntA; probably at least 2 successive AMPylation events occur on Tyr-113. Belongs to the HepT RNase toxin family.