A single residue mutation in Hha preserving structure and binding to H-NS results in loss of H-NS mediated gene repression properties.
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.
Cordeiro
Tiago N
TN
Institute for Research in Biomedicine, Parc Cientific de Barcelona, Baldiri Reixac 10-12, 08028 Barcelona, Spain.
Garcia
Jesús
J
Pons
José-Ignacio
JI
Aznar
Sonia
S
Juárez
Antonio
A
Pons
Miquel
M
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
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