Cloning and characterization of an iron regulated locus, iroA, in Salmonella enterica serovar Choleraesuis.
To identify genes belonging to the Ferric update regulator (Fur) regulon of Salmonella enterica serovar Choleraesuis, the Fur titration assay (FURTA) was used to screen a genomic library for Fur promoters and iron-regulated genes. Fifteen FURTA positive clones were identified from this assay. DNA sequence analysis of these clones showed that 11 out of 15 clones had a Fur binding site (Fur box), and 6 of these clones showed homology to the iron-regulated genes of S. enterica serovar Typhi and/or E. coli. One of these clones (pSC4) was homologous to the iroB gene of the iroA locus of S. enterica serovar Typhi. The iroA locus of S. enterica serovar Choleraesuis was cloned from a lambda-dash library and subjected to DNA sequencing. The complete nucleotide sequence of 9848 bp of the iroA locus of S. enterica serovar Choleraesuis consists of iroB, C, D, E and N genes, which are transcriptionally regulated by Fur. The amino acid sequence of IroB, C, D, E and N was 95%, 86, 89, 96 and 96% identity to that of S. enterica serovar Typhi. The IroN gene was homologous to the family of TonB-dependent outer membrane receptors and the putative virulence factor, IroNE. coli, of the extraintestinal pathogenic E. coli. The convalescent porcine sera contained antibodies against the three major iron-regulated outer membrane proteins of S. enterica serovar Choleraesuis. An insertional inactivation of the iroN gene of S. enterica serovar Choleraesuis by allelic exchange resulted in the loss of expression of the 78 kDa protein. However, this mutant had a similar LD50 to mice compared to the parent strain when given intraperitoneally.
Wu
Wen-Sheng
WS
Department of Veterinary Medicine, National Taiwan University, 142 ZhouShan Road, Taipei 106, Taiwan.
Hsieh
Pei-Chen
PC
Huang
Tzu-Min
TM
Chang
Yung-Fu
YF
Chang
Chao-Fu
CF
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D009154:Mutation; D019151:Peptide Library; D011401:Promoter Regions, Genetic; D019779:Salmonella enterica / Q000235:genetics* / Q000378:metabolism; D017422:Sequence Analysis, DNA
D001425:Bacterial Outer Membrane Proteins; D019151:Peptide Library; C083821:iroA protein, bacteria; D007501:Iron