Essential residues in the H-NS binding site of Hha, a co-regulator of horizontally acquired genes in Enterobacteria

► Hha is a H-NS co-regulator modulating the expresión of horizontally acquired genes. ► H-NS interaction involves a conformational change of Hha. ► We systematically mutated conserved acídic residues in Hha. ► Asp 48 is an essential residue for H-NS binding. ► Mutation of Glu 25 reduces the affinity of H-NS.