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Updated: Jun 27, 2026
Staphylococcus aureus Growth using Human Hemoglobin as an Iron Source
Published on: February 7, 2013
Iron acquisition by the haem-binding Isd proteins in Staphylococcus aureus: studies of the mechanism using magnetic
Michael T Tiedemann1, Naomi Muryoi, David E Heinrichs
1Department of Chemistry, University of Western Ontario, London, Ontario, Canada.
Abstract:
The bacterium Staphylococcus aureus is responsible for numerous hospital-acquired infections ranging from superficial wound lesions to more severe infections such as pneumonia, osteomyelitis and septicaemia and, in some cases, death. The Isd (iron-regulated surface determinant) proteins expressed by S. aureus and select other bacteria are anchored to the bacterial cell wall and membrane and are involved in extracting haem from haemoglobin as an iron source. Our knowledge of the overall haem-scavenging mechanism on the bacterial surface is limited. A detailed description of the haem-binding properties in the transport pathway is critical to our understanding of the mechanism for haem-iron scavenging in S. aureus. Our work involves using a combination of techniques to characterize both the dynamic and steady-state haem-binding properties of these proteins. UV-visible absorption and MCD (magnetic circular dichroism) spectroscopy provide diagnostic spectral data sensitive to the axial ligands, the spin state and oxidation state of the central haem-iron. Electrospray MS provides stoichiometric information on the numbers of haems bound, the effect of haem binding on the overall folding of each protein and kinetic information about the rate of haem binding. Together, these data allow us to address the outstanding questions regarding the mechanism of haem transport via the Isd protein chain in S. aureus.
Insights
Staphylococcus aureus uses iron-regulated surface determinant (Isd) proteins to scavenge iron from hemoglobin. This study characterizes Isd protein haem-binding properties, revealing crucial details about iron acquisition in this common pathogen.
Area of Science:
- Microbiology
- Biochemistry
- Spectroscopy
Background:
- Staphylococcus aureus causes significant hospital-acquired infections.
- Iron acquisition is vital for bacterial survival and virulence.
- The iron-regulated surface determinant (Isd) protein system facilitates iron scavenging from host haemoglobin.
Purpose of the Study:
- To elucidate the haem-binding properties of Staphylococcus aureus Isd proteins.
- To understand the mechanism of haem-iron transport via the Isd protein chain.
Main Methods:
- Utilized UV-visible absorption and magnetic circular dichroism (MCD) spectroscopy to analyze haem-binding.
- Employed electrospray mass spectrometry (MS) to determine stoichiometry and kinetics.
Main Results:
- Characterized dynamic and steady-state haem-binding properties of Isd proteins.
- Obtained spectral data sensitive to haem-iron's electronic and coordination environment.
- Determined the number of haems bound, effects on protein folding, and binding rates.
Conclusions:
- Provided critical insights into the mechanism of haem transport by the Isd protein chain in S. aureus.
- Detailed understanding of haem-iron scavenging is essential for combating S. aureus infections.
