Gut bactericidal protein that selectively kills Gram-positive bacteria by binding to negatively charged lipids on bacterial membranes, leading to bacterial membrane permeabilization and disruption (PubMed:34735226). Specifically binds lipids bearing negatively charged headgroups, such as phosphatidic acid, phosphatidylserine (PS), cardiolipin (CL), and phosphatidylinositol phosphates, but not to zwitterionic or neutral lipids (PubMed:34735226). Induced by type-2 cytokines in response to helminth infection and is required to protect against helminth-induced bacterial invasion of intestinal tissue (By similarity). May also be involved in the development of the cornified envelope of squamous epithelia; however, additional evidences are required to confirm this result in vivo (PubMed:8325635). Present in intestinal secretory epithelial cells and is secreted into the intestinal lumen. Expressed in intestine; selectively expressed in goblet cells. During squamous differentiation of epidermal keratinocytes. Forms five pairs of intrachain disulfide bonds. Belongs to the cornifin (SPRR) family.