Affiliation:
1. Laboratory of Bacterial Toxins, Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland
Abstract
ABSTRACT
This report describes a genetic locus associated with siderophore biosynthesis and transport in
Corynebacterium diphtheriae
. A BLAST search of the
C. diphtheriae
genome identified a seven-gene cluster that included four genes, designated
ciuA, ciuB, ciuC
, and
ciuD
, whose predicted products are related to ABC-type iron transporters. Downstream from
ciuD
is the
ciuE
gene, whose predicted product is similar to the aerobactin biosynthetic enzymes IucA and IucC. The CiuE protein, which has a predicted mass of 121,582 Da and is approximately twice the size of either IucC or IucA, is homologous to each of these proteins in both its N- and C-terminal regions.
C. diphtheriae ciuE
deletion mutants exhibited a defect in siderophore production, iron uptake, and growth in low-iron medium. Mutations in the
ciuA
gene, whose predicted product is a lipoprotein component of an iron transport system, resulted in a severe defect in iron uptake and reduced ability to use the
C. diphtheriae
siderophore as an iron source. Site-directed mutations in
irp6A
, a gene previously reported to be associated with siderophore transport, had no effect on iron uptake or the utilization of the
C. diphtheriae
siderophore as an iron source. Transcriptional analysis demonstrated that expression of
ciuA
and
ciuE
is DtxR and iron regulated, and DNase I protection experiments confirmed the presence of DtxR binding sites upstream from each of these genes. Thus, this iron- and DtxR-regulated gene cluster is involved in the synthesis and transport of the
C. diphtheriae
siderophore.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
50 articles.
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