Probable nuclease member of antiviral defense system retron Eco8, composed of an reverse transcriptase (RT), this nuclease and a non-coding RNA (ncRNA) encoded between them. Expression of retron Eco8 confers protection against bacteriophages T4, T6, T7 and SECphi4, SECphi6 and SECphi18. At multiplicity of infection (MOI) of 0.02 cultures slow growth when infected with SECphi4 but do not collapse, at MOI 2 cultures collapse. When the retron is cloned in another E.coli strain synthesizes msDNA (a branched RNA linked by a 2',5'-phosphodiester bond to a single-stranded DNA). The retron transcript serves as primer and template to the reaction, and codes for the RT. Probably binds 2 metal cations. Homodimer. Belongs to the class 1 OLD nuclease family.