Reverse transcriptase (RT) component of antiviral defense system retron Ec73, composed of a non-coding RNA (ncRNA) followed by a ribosyltransferase/DNA-binding protein then a reverse transcriptase (RT). Expression of this retron confers protection against bacteriophages SECphi4, SECphi6, SECphi27 and P1. At multiplicity of infection (MOI) of 0.02 cultures grow normally when infected with SECphi4 without collapsing, at MOI 2 cultures enter growth stasis (PubMed:33157039). Responsible for synthesis of msDNA-Ec73 (a branched molecule with RNA linked by a 2',5'-phosphodiester bond to ssDNA). The retron transcript serves as primer (from a conserved internal G residue) and template for the reaction, and codes for the RT (PubMed:1712012, PubMed:10531319, PubMed:1709758, PubMed:7529762). Recognizes only its cognate RNA as a primer template (PubMed:10531319). a 2'-deoxyribonucleoside 5'-triphosphate + DNA(n) = diphosphate + DNA(n+1) The C-terminal domain (residue 247-316) is required to recognize RNA. Bacteria no longer produce msDNA. Part of pro-retronphage phiR73, which is homologous to bacteriophage P4 (PubMed:1712012). With the help of P2 bacteriophage, is excised and packaged into an infectious virion. Retronphage phiR73 can lysogenize a new host strain, reintegrating its genome into the selC gene of the host chromosome and enabling the newly formed lysogens to produce msDNA-Ec73 (PubMed:1709758). Belongs to the bacterial reverse transcriptase family.