Tight regulation of intracellular metal ion concentrations is crucial for any organism’s survival and plays a central role in the host-pathogen interaction. While metal homeostasis has been studied in different model organisms for a long time, evidence that different metals are not regulated independently from each other has only recently begun to emerge. Manganese and iron are particularly interesting because, although they have fairly similar chemical properties, they play opposing roles in the cell when it comes to oxidative stress: iron exacerbates oxidative stress, whereas manganese protects against it. Their intracellular concentrations are therefore cross-regulated.
The key players in prokaryotic metal homeostasis are metal-sensing transcription factors which regulate the expression of target genes such as metal transporters. We investigate the structure and function of the manganese and iron sensors in an actinomycete model organism, Saccharopolyspora erythraea, using a dual approach. We isolate the metal sensors in order to study them in vitro using biochemical and biophysical techniques, and we genetically manipulate their host organism in order to understand their function in vivo. We aim to understand how the metal sensors bind and distinguish between different metal ions and regulate their target genes.
Our methods include molecular biology, protein production in different expression systems, protein purification, X-ray crystallography and small-angle X-ray scattering, as well as different biochemical and biophysical techniques to study DNA and metal ion binding, such as fluorescence spectroscopy and isothermal titration calorimetry (ITC).
The overall goal of our research is to unravel the links between manganese and iron homeostasis and the oxidative stress response in actinomycetes. Metal homeostasis plays an important role in the production of medically interesting secondary metabolites by actinomycetes, such as the broad-spectrum antibiotic erythromycin by S. erythraea itself, as well as in virulence of pathogenic actinomycetes such as Mycobacterium tuberculosis. A better understanding of metal homeostasis in actinomycetes can therefore help in the development of new antibiotics in two ways, by enabling the production of novel secondary metabolites, as well as by identifying potential drug targets.