Affiliation:
1. Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College Dublin, Dublin, Ireland
2. Department of Molecular Medicine, Pavia, Italy
Abstract
ABSTRACT
Staphylococcus lugdunensis
is the only coagulase-negative
Staphylococcus
species with a locus encoding iron-regulated surface determinant (Isd) proteins. In
Staphylococcus aureus
, the Isd proteins capture heme from hemoglobin and transfer it across the wall to a membrane-bound transporter, which delivers it into the cytoplasm, where heme oxygenases release iron. The Isd proteins of
S. lugdunensis
are expressed under iron-restricted conditions. We propose that
S. lugdunensis
IsdB and IsdC proteins perform the same functions as those of
S. aureus
.
S. lugdunensis
IsdB is the only hemoglobin receptor within the
isd
locus. It specifically binds human hemoglobin with a dissociation constant (
K
d
) of 23 nM and transfers heme on IsdC. IsdB expression promotes bacterial growth in an iron-limited medium containing human hemoglobin but not mouse hemoglobin. This correlates with weak binding of IsdB to mouse hemoglobin
in vitro
. Unlike IsdB and IsdC, the proteins IsdJ and IsdK are not sorted to the cell wall in
S. lugdunensis
. In contrast, IsdJ expressed in
S. aureus
and
Lactococcus lactis
is anchored to peptidoglycan, suggesting that
S. lugdunensis
sortases may differ in signal recognition or could be defective. IsdJ and IsdK are present in the culture supernatant, suggesting that they could acquire heme from the external milieu. The IsdA protein of
S. aureus
protects bacteria from bactericidal lipids due to its hydrophilic C-terminal domain. IsdJ has a similar region and protected
S. aureus
and
L. lactis
as efficiently as IsdA but, possibly due to its location, was less effective in its natural host.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
44 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献