HDEA, a periplasmic protein that supports acid resistance in pathogenic enteric bacteria

The X-ray crystal structure of the Escherichia coli stress response protein HDEA has been determined at 2.0 Angstrom resolution. The single domain alp ha-helical protein is found in the periplasmic space, where it supports an acid resistance phenotype essential for infectivity of enteric bacterial pa thogens, such as Shigella and E. coli. 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. We suggest that HDE A may support chaperone-like functions during the extremely acidic conditio ns. (C) 2000 Academic Press.