title: A single residue mutation in Hha preserving structure and binding to H-NS results in loss of H-NS mediated gene repression properties.
abstract: In this study, we report that a single mutation of cysteine 18 to isoleucine (C18I) in Escherichia coli Hha abolishes the repression of the hemolysin operon observed in the wild-type protein. The phenotype also includes a significant decrease in the growth rate of E. coli cells at low ionic strength. Other substitutions at this position (C18A, C18S) have no observable effects in E. coli growth or hemolysin repression. All mutants are stable and well folded and bind H-NS in vitro with similar affinities suggesting that Cys 18 is not directly involved in H-NS binding but this position is essential for the activity of the H-NS/Hha heterocomplexes in the regulation of gene expression.
authors.affiliation: Institute for Research in Biomedicine, Parc Cientific de Barcelona, Baldiri Reixac 10-12, 08028 Barcelona, Spain.
authors.forename: Tiago N
authors.initials: TN
authors.lastname: Cordeiro
authors.forename: Jesús
authors.initials: J
authors.lastname: Garcia
authors.forename: José-Ignacio
authors.initials: JI
authors.lastname: Pons
authors.forename: Sonia
authors.initials: S
authors.lastname: Aznar
authors.forename: Antonio
authors.initials: A
authors.lastname: Juárez
authors.forename: Miquel
authors.initials: M
authors.lastname: Pons
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D003545:Cysteine / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D006460:Hemolysin Proteins / Q000235:genetics; D009876:Operon; D017354:Point Mutation; D011487:Protein Conformation; D017510:Protein Folding
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C031908:H-NS protein, bacteria; D006460:Hemolysin Proteins; C079209:hha protein, E coli; D003545:Cysteine