This family of proteins is found in bacteria. Proteins in this family are typically between 328 and 381 amino acids in length. There is a conserved LGDG sequence motif. Clostridial species have a layer of surface proteins surrounding their membrane. This layer is comprised of a high molecular weight protein and a low molecular weight protein. This domain is the N terminal domain of the low molecular weight protein. It is a structural domain.

1: Structural insights into the molecular organization of the S-layer from Clostridium difficile. Fagan RP, Albesa-Jove D, Qazi O, Svergun DI, Brown KA, Fairweather NF; Mol Microbiol. 2009;71:1308-1322. PMID:19183279