This is an immunoglobulin like domain found in ChiW, a chitinase with high activity towards various chitins. ChiW has a multi-modular architecture composed of six domains to function efficiently on the cell surface: a right-handed beta-helix domain (carbohydrate-binding module family 54, CBM-54), a Gly-Ser-rich loop, 1st immunoglobulin-like (Ig-like) fold domain, 1st beta/alpha-barrel catalytic domain (glycoside hydrolase family 18, GH-18), 2nd Ig-like fold domain and 2nd beta/alpha-barrel catalytic domain (GH-18) [1].

1: Crystal Structure of Chitinase ChiW from Paenibacillus sp. str. FPU-7 Reveals a Novel Type of Bacterial Cell-Surface-Expressed Multi-Modular Enzyme Machinery. Itoh T, Hibi T, Suzuki F, Sugimoto I, Fujiwara A, Inaka K, Tanaka H, Ohta K, Fujii Y, Taketo A, Kimoto H; PLoS One. 2016;11:e0167310. PMID:27907169