HdeA (hns-dependent expression protein A) is a single domain alpha-helical protein localised in the periplasmic space. HdeA is involved in acid resistance essential for infectivity of enteric bacterial pathogens. Functional studies demonstrate that HdeA is activated by a dimer-to-monomer transition at acidic pH, leading to suppression of aggregation by acid-denatured proteins. The gene encoding HdeA was initially identified as part of an operon regulated by the nucleoid protein H-NS [1,2]. This family also contains HdeB [3].

1: HDEA, a periplasmic protein that supports acid resistance in pathogenic enteric bacteria. Gajiwala KS, Burley SK; J Mol Biol 2000;295:605-612. PMID:10623550

2: Crystal structure of Escherichia coli HdeA. Yang F, Gustafson KR, Boyd MR, Wlodawer A; Nat Struct Biol 1998;5:763-764. PMID:9731767

3: Escherichia coli HdeB is an acid stress chaperone. Kern R, Malki A, Abdallah J, Tagourti J, Richarme G; J Bacteriol. 2007;189:603-610. PMID:17085547