BREX systems (bacteriophage exclusion) provide immunity against bacteriophage. Part of a type 2 BREX system (Probable). Previously called the phage growth limitation (Pgl) system, it confers protection against bacteriophage phiC31. The bacteria allows one cycle of phage infection, but subsequent cycles are impaired, protecting the original bacterial colony (PubMed:7642495). The system undergoes high rates (10(-3) to 10(-4)) of phase reversion, i.e. loss and regain of phiC31 resistance (PubMed:8446035). When the pglW-pglX-pglY-pglZ genes are transformed into a susceptible S.lividans (strain 1326) they confer resistance to infection by phage phiC31 and phiBT1; all 4 genes are necessary (PubMed:11972785). Probably an antitoxin component of a type II toxin-antitoxin (TA) system. Inhibits the toxic activity of its cognate toxin PglX. Constitutively expressed, not induced by bacteriophage phiC31, probably part of a pglY-pglZ operon. Deletion of the C-terminus (residues 835-974) still allows this protein confer phage resistance and act as an antitoxin to PglX. Identified by mass spectrometry as a slightly larger than expected protein, suggesting it may be modifed with a low molecular weight adduct. Strain is no longer resistant to plaque formation by bacteriophage phiC31 (a Pgl- phenotype). Belongs to the alkaline phosphatase superfamily.