Protein Structure and Interactions

Biosynthesis of the fungal cell wall and structural analysis of the RodA hydrophobin from Aspergillus fumigatus conidia
(C. Simenel, Arianne Pillé, M. Delepierre, J.I. Guijarro)
A. fumigatus is an opportunistic pathogen that causes invasive mycosis which show a high incidence and mortality among immunocompromised people. The mould grows in the soil and spreads through the air in the form of conidia (spores). In collaboration with the team of Jean-Paul Latgé (Aspergillus Unit, Institut Pasteur), we are interested in the cell wall biosynthesis and structure and in the hydrophobic rodlet layer that covers the spores, which constitute the invasive form of the mould.
The backbone of the fungal cell wall is mainly composed of chitin-glucan complexes. The branching of these carbohydrate polymers confers rigidity to the cell wall, an essential feature for fungal growth and survival. Our objective is to analyze the enzymes and reactions associated with chitin and glucan synthesis, branching and cross-linking to understand the assembly of the cell wall polysaccharide structure. We use NMR as an analytical tool to identify the monosaccharide residues, their anomeric configuration and the branching points of the cell wall carbohydrates.
The conidia cell wall is coated by a hydrophobic rodlet layer formed by the hydrophobin protein RodA, which self-assembles into amyloid-like fibrils on the spore surface. This hydrophobic rodlet coating, on the one hand allows the dispersal of the spores, and on the other hand masks the recognition of antigens and allergens and renders the spores immunologically inert. Our main objective is to investigate the solution structure of RodA, the transition from the soluble form to the insoluble rodlet state and the structure of hydrophobin within the rodlets.

Putative transcription factors from hyperthermophilic archaea and their viruses
(F. Guillière, J. I. Guijarro)
Hyperthermophilic archaea that shrive in hot springs (> 80°C) are infected by viruses, which show an exceptional diversity and differ greatly from known bacterial and eukaryal viruses. Within the frame of the characterisation of these unique and interesting viruses of which little is known, in recent years we have focused on proteins that were likely to be involved in transcription regulation, which is an important phenomenon during infection. In collaboration with the team of D. Prangishvili (Institut Pasteur), we have coupled structural and functional data (protein structures, protein-DNA interactions, search of DNA targets, in vitro transcription assays...) to characterise transcription regulators and thereby better understand at the molecular level the regulation of the archaeal virus cycle, a poorly explored domain of archaeal virology.