This family of proteins is functionally uncharacterized. This family of proteins is found in Bacteroides species. Proteins in this family are typically between 234 and 260 amino acids in length. These proteins possess an N-terminal lipoprotein attachment site. The family includes NigD a protein found in the Nig operon that encodes a bacteriocin called nigrescin. It has been suggested that NigD may be the immunity protein for nigrescin (NigC) because it is directly downstream. This domain has an OB fold.