Iron is an essential cofactor for numerous enzymatic reactions, but its solubility is very low. To satisfy their need on iron, bacteria have developped various systems to solubilize and storage it. Our group first discovered an new system to acquire haem. Haem is an iron source found in several proteins among which the hemoglobin is the best known. This new Haem Acquisition System (HAS) was found in Serratia marcescens bacteria, but it is also present in others species like Erwinia carotovora, Pseudomonas aeruginosa, Pseudomonas fluorescens, Yersinia enterocolitica and Yersinia pestis. Our studies cover the regulation of gene expression as well as the elucidation of the mecanism of action of each of the protein of the HAS system.
The Has system, expressed when bacteria meet an iron deprived environment, allows the extracellular secretion of a protein with a high affinity for haem, called hemophore (HasA). To be secreted this protein use an ABC secretion pathway, called ABC because it uses an ABC protein. The ATP-Binding Cassette (ABC) systems constitute the largest family of paralogues ever found. They are involved in a variety of biological processes, including not only transport across membranes, but also regulation of translation and transcription or DNA repair. In humans, 15 severe inherited diseases (including cystic fibrosis and leukodystrophy) are caused by the dysfunction of ABC transporters. In bacteria some ABC systems are directly involved in antibiotics multiresistance of pathogens germs.
One of our major research project concerns the study of the HAS system.
A second project is about the study of the mecanism of hemophore secretion and especially how it does interact with the ABC protein.
A third project is about functionnal and phylogenetic studies of ABC systems.
Last, a fourth project just started about a new regulation pathway in iron acquisition in Escherichia coli.
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