Plays a key role in the innate immune response following bacterial infection by inserting into the bacterial surface to form pores (By similarity). By breaching the surface of phagocytosed bacteria, allows antimicrobial effectors to enter the bacterial periplasmic space and degrade bacterial proteins such as superoxide dismutase sodC which contributes to bacterial virulence (By similarity). Shows antibacterial activity against a wide spectrum of Gram-positive, Gram-negative and acid-fast bacteria (PubMed:23753625, PubMed:26402460, PubMed:30609079, PubMed:28422754, PubMed:33224153). Reduces the viability of the intracytosolic pathogen L.monocytogenes by inhibiting acidification of the phagocytic vacuole of host cells which restricts bacterial translocation from the vacuole to the cytosol (By similarity). Required for the antibacterial activity of reactive oxygen species and nitric oxide (By similarity). Bacterial infection induces translocation of the cytoplasmic vesicles to bacterium-containing phagocytic vesicles and fusing of the vesicles. Expressed constitutively in a variety of cell types including macrophages, natural killer cells, neutrophils, keratinocytes and monocytes (PubMed:26402460, PubMed:28705375, PubMed:7888681). In skin, expressed in both hematopoietic and non-hematopoietic cells with expression detected in a variety of cell types including keratinocytes, fibroblasts and endothelial cells (PubMed:30609079). By wounding; increased levels are observed in hematopoietic cells 48 hours after wounding (PubMed:30609079). Following wounding, repressed by infection with S.aureus (PubMed:30609079). Isoform 1: By lipopolysaccharide and TNF (PubMed:28705375). Isoform 2: By lipopolysaccharide and TNF (PubMed:28705375). Monoubiquitinated in response to bacterial infection; ubiquitination is required for vesicular localization and antibacterial activity and can be blocked by bacterial cell cycle inhibiting factor (cif) (By similarity). The disease is caused by variants affecting the gene represented in this entry. Lacks the C-terminal transmembrane domain. Belongs to the MPEG1 family. Extended N-terminus.