Both GamL and GamS bind to host RecBCD nuclease and inhibit its activities, protecting the viral DNA against RecBCD mediated degradation (PubMed:2943636, PubMed:4275917, PubMed:126236, PubMed:1653221, PubMed:17544443). Isoform GamS mimics DNA, preventing RecBCD from binding DNA (PubMed:17544443, PubMed:28009252). Expression of this protein in E.coli renders cells more sensitive to fluoroquinolone antibiotics (which inhibit topoisomerases and induce dsDNA breaks) (PubMed:28009252). Frameshift mutations that delete most of this protein (starting from position 78 or 97 of GamL) allow the bacteriophage to overcome the retron Ec48 bacteriophage defense system. Overexpression of the wild-type gam protein in E.coli with an intact Ec48 retron leads to a dramatic decrease in cell growth, the frameshift mutants do not have this effect (PubMed:33157039). Homodimer (PubMed:126236, PubMed:17544443, PubMed:28009252). Interacts with host RecBCD without displacing any of the subunits; this interaction prevents RecBCD from binding to DNA (PubMed:1653221, PubMed:17544443, PubMed:28009252). The GamS isoform makes extensive contacts with RecB, and inserts deeply into the RecBCD complex (PubMed:28009252). 2 forms, GamL and GamS are isolated from overproducing cells; the shorter form (GamS) is more abundant. As both have good ribosome-binding sites they may be independently translated. GamS is processed at the N-terminus and starts on Tyr-44 and Ile-46; both start sites are present in equal amounts (PubMed:1653221). In cells with an induced lambda prophage a protein consistent with the size of GamL was isolated (PubMed:126236). Originally (PubMed:6458018) the gam gene product was assigned to the sequence shown and it was suggested that the gene kil protein is encoded from within this gene and corresponds to residues 41-138 (now called GamS). For an alternative assignment of this gene see the entry for the kil gene protein of lambda. Truncated N-terminus.