Arginine 66 residue of Fur is required for the regulatory function of this protein in the acid adaptation mechanism of Helicobacter pylori.
BACKGROUND
Helicobacter pylori colonizes the gastric mucosa and must survive the acid pH of that environment. Like other enteric bacterial pathogens, including Salmonella enterica, H. pylori develops an acid tolerance response that is dependent on the function of the transcriptional regulator protein Fur.


OBJECTIVE
To explore by site-directed mutagenesis whether two particular amino acid residues in the amino acid sequence of the H. pylori Fur protein, arginine 66 and histidine 99, are involved in the acid response mechanism in this bacterium.


METHODS
Complementation assays in Escherichia coli H1780 (fur null mutant) both with plasmids carrying the H. pylori fur gene bearing substitution mutations R66A or H99A or R66A/H99A and with the H. pylori Fur-R66A mutant were conducted. Wild-type and mutated Fur proteins from H. pylori were assayed by using the fiu::lacZ reporter gene in the E. coli H1780 heterologous system at various pH and iron concentrations.


RESULTS
Both bacterial growth and repression of the reporter gene were impaired under acid conditions in E. coli H1780 complemented with pUC19-fur-R66A. Also, in the H. pylori Fur-R66 strain bacterial growth and speA gene expression were impaired under acid conditions.


CONCLUSIONS
Arginine 66 but not histidine 99 in H. pylori Fur is required for the regulatory function of the Fur protein in the acid adaptation mechanism of the bacterium.
Programa de Biología Celular y Molecular, ICBM, Facultad de Medicina, Universidad de Chile, Avenida Independencia 1027, Casilla 70086, Santiago-7, Chile. htoledo@med.uchile.cl
Héctor
H
Toledo
Carlos
C
Villafaena
Manuel
M
Valenzuela
Remigio
R
López-Solís
D000595:Amino Acid Sequence; D001120:Arginine / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D005753:Gastric Mucosa / Q000382:microbiology; D015964:Gene Expression Regulation, Bacterial; D016481:Helicobacter Infections / Q000382:microbiology; D016480:Helicobacter pylori / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D006639:Histidine / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D016415:Sequence Alignment; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D006639:Histidine; D001120:Arginine