Many bacteria are covered in a layer of surface-associated polysaccharide called the capsule. These capsules can be divided into four groups depending upon the organisation of genes responsible for capsule assembly, the assembly pathway and regulation [1]. This family plays a role in group 4 capsule biosynthesis [2]. These proteins have a beta-grasp fold [3]. Two beta-grasp domains, D2 and D3, are arranged in tandem. There is a C-terminal amphipathic helix which packs against D3. A helical hairpin insert in D2 binds to D3 and constrains its position, a conserved arginine residue at the end of this hairpin is essential for structural integrity [4]. This entry represents D2 domain found at the N-terminal [4].

1: Structure, assembly and regulation of expression of capsules in Escherichia coli. Whitfield C, Roberts IS; Mol Microbiol. 1999;31:1307-1319. PMID:10200953

2: Identification of an Escherichia coli operon required for formation of the O-antigen capsule. Peleg A, Shifrin Y, Ilan O, Nadler-Yona C, Nov S, Koby S, Baruch K, Altuvia S, Elgrably-Weiss M, Abe CM, Knutton S, Saper MA, Rosenshine I; J Bacteriol. 2005;187:5259-5266. PMID:16030220

3: A novel superfamily containing the beta-grasp fold involved in binding diverse soluble ligands. Burroughs AM, Balaji S, Iyer LM, Aravind L; Biol Direct. 2007;2:4-4. PMID:17250770

4: Crystal structure of E. coli group 4 capsule protein GfcC reveals a domain organization resembling Wza. Sathiyamoorthy K, Mills E, Franzmann TM, Rosenshine I, Saper MA; Biochemistry 2011;0:0-0. PMID:21449614