1 research outputs found
An ABC Transporter with Two Periplasmic Binding Proteins Involved in Iron Acquisition in <i>Pseudomonas aeruginosa</i>
Pyoverdine I is the main siderophore secreted by <i>Pseudomonas aeruginosa</i> PAO1 to obtain access to iron. After
extracellular iron chelation, pyoverdine-Fe uptake into the bacteria
involves a specific outer-membrane transporter, FpvA. Iron is then
released in the periplasm by a mechanism involving no siderophore
modification but probably iron reduction. The proteins involved in
this dissociation step are currently unknown. The pyoverdine locus
contains the <i>fpvCDEF</i> operon, which contains four
genes. These genes encode an ABC transporter of unknown function with
the distinguishing characteristic of encompassing two periplasmic
binding proteins, FpvC and FpvF, associated with the ATPase, FpvE,
and the permease, FpvD. Deletion of these four genes partially inhibited
cytoplasmic uptake of <sup>55</sup>Fe in the presence of pyoverdine
and markedly slowed down the <i>in vivo</i> kinetics of
iron release from the siderophore. This transporter is therefore involved
in iron acquisition by pyoverdine in <i>P. aeruginosa</i>. Sequence alignments clearly showed that FpvC and FpvF belong to
two different subgroups of periplasmic binding proteins. FpvC appears
to be a metal-binding protein, whereas FpvF has homology with ferrisiderophore
binding proteins. <i>In vivo</i> cross-linking assays and
incubation of purified FpvC and FpvF proteins showed formation of
complexes between both proteins. These complexes were able to bind <i>in vitro</i> PVDI-Fe, PVDI-Ga, or apo PVDI. This is the first
example of an ABC transporter involved in iron acquisition <i>via</i> siderophores, with two periplasmic binding proteins
interacting with the ferrisiderophore. The possible roles of FpvCDEF
in iron uptake by the PVDI pathway are discussed