Fur-independent induction of Helicobacter pylori flavodoxin-encoding gene (fldA) under iron starvation.
OBJECTIVE
Helicobacter pylori infection is associated with a variety of diseases including gastric cancer. Flavodoxin is an electron transfer protein containing a flavin mononucleotide prosthetic group and substituted an iron-containing electron transfer protein under iron-limiting conditions. H. pylori flavodoxin has been reported but its pathogenic role is unclear. The aim of this study is to understand a pathogenic role of H. pylori flavodoxin under iron-limiting condition.


METHODS
The flavodoxin-encoding gene (fldA) was cloned from one of clinical H. pylori isolates (DU17) and its transcript was quantified by primer extension, Northern hybridization, and real-time polymerase chain reaction in different concentrations of an iron chelator. The fldA transcript was also quantified in H. pylori ATCC 700392, lacking a ferric uptake regulatory (fur) protein.


RESULTS
Nucleotide sequence of the fldA from H. pylori DU17 revealed a 492-bp (164 amino acids) open reading frame with a deduced amino acid sequence having 97% identity to that from the complete genomic sequence of H. pylori 26695. The deduced promoter [-35, -10, and +1] of the fldA was 56-bp upstream from the first codon of FldA. The fldA transcript (approximately 0.55-kb) was induced up to 14-fold in both wild-type and fur-knocked-out strains under iron-limiting conditions, suggesting that the fldA induction is independent to the Fur protein.


CONCLUSIONS
The fldA gene may play an important role in iron starvation conditions.
Kwon
Dong H
DH
Department of Biology, Long Island University, Brooklyn, New York 11201, USA. dong.kwon@liu.edu
Versalovic
James
J
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D005420:Flavoproteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D016481:Helicobacter Infections / Q000382:microbiology*; D016480:Helicobacter pylori / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007501:Iron / Q000378:metabolism*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
D001426:Bacterial Proteins; D005420:Flavoproteins; C120194:FldA protein, Bacteria; D012097:Repressor Proteins; C068477:ferric uptake regulating proteins, bacterial; D007501:Iron