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 (By similarity). Induced by type-2 cytokines in response to helminth infection and is required to protect against helminth-induced bacterial invasion of intestinal tissue (PubMed:34735226). 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 (By similarity). Present in intestinal secretory epithelial cells and is secreted into the intestinal lumen. By type-2 cytokines IL4 and IL13 in response to helminth infection. Forms five pairs of intrachain disulfide bonds. Mice lacking Sprr2a1, Sprr2a2 and Sprr2a3 show an expansion of Gram-positive bacteria in the small intestinal lumen and mucus layer (PubMed:34735226). Mice were born in normal Mendelian ratios, are healthy and show normal intestinal morphology with no signs of inflammation in normal conditions (PubMed:34735226). They however show an increased abundance of Gram-positive bacteria in the small intestinal lumen, with a marked increase in the relative abundance of Lactobacillus, Turicibacter, and C.arthromitus (PubMed:34735226). At the same time, a reduction in the abundance of Bacteroidetes, a class of Gram-negative bacteria is observed (PubMed:34735226). Mice are more susceptible to L. monocytogenes infection (PubMed:34735226). Belongs to the cornifin (SPRR) family.