Functional membrane microdomains and the hydroxamate siderophore transporter ATPase FhuC govern Isd-dependent heme acquisition in Staphylococcus aureus
Curation statements for this article:-
Curated by eLife
eLife assessment:
In this fundamental manuscript, the authors provide compelling evidence that a housekeeping ATPase is required for heme utilization in the important pathogen Staphylococcus aureus through its interaction with the canonical heme transporter in this organism. The authors convincingly show that this complex associates with functional membrane microdomains and thus establishes a new paradigm for regional localization of the heme transport system in the staphylococci. The work will be of interest to microbiologists, particularly those studying transport for macromolecules.
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- Microbiology and Infectious Disease (eLife)
Abstract
Sufficient access to transition metals such as iron is essential for bacterial proliferation and their active limitation within host tissues effectively restricts infection. To overcome iron limitation, the invasive pathogen Staphylococcus aureus uses the iron-regulated surface determinant (Isd) system to acquire hemoglobin-derived heme. While heme transport over the cell wall is well understood, its transport over the membrane is hardly investigated. In this study, we show the heme-specific permease IsdF to be energized by the general ATPase FhuC. Additionally, we show that IsdF needs appropriate location within the membrane for functionality. The membrane of S. aureus possesses special compartments (functional membrane microdomains [FMMs]) to organize membrane complexes. We show IsdF to be associated with FMMs, to directly interact with the FMM scaffolding protein flotillin A (FloA) and to co-localize with the latter on intact bacterial cells. Additionally, Isd-dependent bacterial growth required FMMs and FloA. Our study shows that Isd-dependent heme acquisition requires a highly structured cell envelope to allow coordinated transport over the cell wall and membrane and it gives the first example of a bacterial nutrient acquisition system that depends on FMMs.
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eLife assessment:
In this fundamental manuscript, the authors provide compelling evidence that a housekeeping ATPase is required for heme utilization in the important pathogen Staphylococcus aureus through its interaction with the canonical heme transporter in this organism. The authors convincingly show that this complex associates with functional membrane microdomains and thus establishes a new paradigm for regional localization of the heme transport system in the staphylococci. The work will be of interest to microbiologists, particularly those studying transport for macromolecules.
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Reviewer #1 (Public Review):
In this manuscript, the authors set out to identify the energy-generating protein responsible for powering heme transport through the Isd system of Staphylococcus aureus.
The manuscript convincingly demonstrates that FhuC is required for heme iron utilization and presents strong data to implicate FhuC in binding to IsdF. The authors report that IsdF localizes to functional membrane microdomains in S. aureus. These experiments would benefit from controls showing that the DRM fraction contains the functional membrane microdomains and that the fractionation was successful.
The authors also present strong data demonstrating that loss of floA prevents IsdF incorporation into the membrane although these data would also benefit from genetic complementation.
In a surprising result, the authors report that the IsdA …
Reviewer #1 (Public Review):
In this manuscript, the authors set out to identify the energy-generating protein responsible for powering heme transport through the Isd system of Staphylococcus aureus.
The manuscript convincingly demonstrates that FhuC is required for heme iron utilization and presents strong data to implicate FhuC in binding to IsdF. The authors report that IsdF localizes to functional membrane microdomains in S. aureus. These experiments would benefit from controls showing that the DRM fraction contains the functional membrane microdomains and that the fractionation was successful.
The authors also present strong data demonstrating that loss of floA prevents IsdF incorporation into the membrane although these data would also benefit from genetic complementation.
In a surprising result, the authors report that the IsdA protein is not localized in the functional membrane microdomains which are confounding since IsdA is modeled to work in concert with IsdF. These data suggest there is much more to learn regarding the spatial distribution of this transport system.
Finally, the authors report that FMMs are required for heme transport in the related organism Staphylococcus lugdunensis demonstrating the conservation of this localization across the genus.
Taken together, these exciting and significant data reveal how the canonical heme transporter of S. aureus is regionally localized and acquires energy for heme transport across the membrane.
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Reviewer #2 (Public Review):
The manuscript entitled 'Functional membrane microdomains and the hydroxamate siderophore transporter ATPase FhuC govern Isd-dependent heme acquisition in Staphylococcus aureus' investigates the heme transport over the bacterial cell membrane. The novelty of this paper is proving the requirement of a highly structured cell envelope that depends on functional membrane microdomains FMMs for bacterial nutrient acquisition. The authors showed that the heme-specific permease (IsdF) is associated with FMMs, to directly interact with the FMM scaffolding protein flotillin A (FloA) and to co-localize with the latter on intact bacterial cells since IsdF needs an appropriate location within the membrane for functionality.
The strengths of the manuscript:
It provides new evidence on the different mechanisms used by S. …
Reviewer #2 (Public Review):
The manuscript entitled 'Functional membrane microdomains and the hydroxamate siderophore transporter ATPase FhuC govern Isd-dependent heme acquisition in Staphylococcus aureus' investigates the heme transport over the bacterial cell membrane. The novelty of this paper is proving the requirement of a highly structured cell envelope that depends on functional membrane microdomains FMMs for bacterial nutrient acquisition. The authors showed that the heme-specific permease (IsdF) is associated with FMMs, to directly interact with the FMM scaffolding protein flotillin A (FloA) and to co-localize with the latter on intact bacterial cells since IsdF needs an appropriate location within the membrane for functionality.
The strengths of the manuscript:
It provides new evidence on the different mechanisms used by S. aureus to acquire iron. These new findings are essential in understanding the way this bacterium survives nutritional immunity and thus can be a target for novel therapeutic approaches.
All the results were based on the necessary molecular techniques that strongly support the conclusions.The weaknesses of the manuscript:
More details concerning different strategies of iron acquisition should be mentioned in the introduction.
Additional bibliographic literature is needed for explaining what unknown ATPase partially substitutes for the function of FhuC.
More experiments are needed in order to verify the speculations presented in the last part of the manuscript. -
