This domain is found in Endo-alpha-N-acetylgalactosaminidase (SpGH101) from Streptococcus pneumoniae and similar bacterial proteins. This protein, which belongs to the Glycoside Hydrolase Family 101 (GH101), is a virulence factor. It hydrolyses the T-antigen disaccharide from extracellular host glycoproteins to aid colonization. SpGH101 has seven domains. This entry represents the helical bundle domain, which consists of three alpha-helices that form an interface [1,2].

1: The structural basis for T-antigen hydrolysis by Streptococcus pneumoniae: a target for structure-based vaccine design. Caines ME, Zhu H, Vuckovic M, Willis LM, Withers SG, Wakarchuk WW, Strynadka NC; J Biol Chem. 2008;283:31279-31283. PMID:18784084

2: Identification and molecular cloning of a novel glycoside hydrolase family of core 1 type O-glycan-specific endo-alpha-N-acetylgalactosaminidase from Bifidobacterium longum. Fujita K, Oura F, Nagamine N, Katayama T, Hiratake J, Sakata K, Kumagai H, Yamamoto K; J Biol Chem. 2005;280:37415-37422. PMID:16141207