This is the N-terminal extracellular adhesion domain of Sialic acid binding adhesin (SabA) present in Helicobacter pylori. The N-terminal domain of SabA functions as a sugar-binding adhesion domain with conserved disulfide bonds. Notably, these amino acid residues are not only conserved among SabA orthologs but also between SabA and BabA [1].

1: The three-dimensional structure of the extracellular adhesion domain of the sialic acid-binding adhesin SabA from Helicobacter pylori. Pang SS, Nguyen ST, Perry AJ, Day CJ, Panjikar S, Tiralongo J, Whisstock JC, Kwok T; J Biol Chem. 2014;289:6332-6340. PMID:24375407