Main Research Lines
Host-Pathogen interactions and the innate immunity
The interactions that occur at the interface between the human host and the myriad bacterial microorganisms with which we come into daily contact constitute a topic of profound significance, both at a fundamental biological level and as an area of expanding medical interest. The complement system of the innate immunity stands as one of the first defence barriers against pathogens. It is a collection of soluble and membrane-associated proteins that monitor the blood and tissue interstitial fluids for pathogens, apoptotic cells and immune complexes. Pathogens have evolved sophisticated molecular weaponry that allows them to escape surveillance from the complement system, a strategy designated as immunoevasion. In this context, we are focused in elucidating the structures and mechanistic details of the complement system components and their protein complexes with virulence factors with immunoevasive properties. Increasing our understanding of these processes at the atomic level is crucial to develop potential treatments against many diseases.
Sulfur trafficking and tRNA hypermodifications
Across all domains of life, organisms have evolved complex systems of interacting proteins with the task of mobilising sulfur atoms from the amino acid L-cysteine in the form of highly reactive persulfides (-S-S–), which are then channeled to other proteins until they reach their ultimate destination — iron-sulfur (Fe-S) clusters, sulfur-containing vitamins, cofactors and lipids, or thiol-containing tRNA hypermodified ribonucleosides. Our research has focused on the minimalistic CSD (Cysteine Sulfinate Desulfinase) system of the model bacterium E. coli, which encodes a cysteine desulfurase (CsdA), a sulfur acceptor (CsdE), and TcdA, an E1-like enzyme capable of cyclising the N6-threonylcarbamoyl adenosine (t6A) present at the A37 position of the anti-codon stem loop (ASL) motif of tRNA(ANN) molecules.
We have determined the crystal structures of all three component proteins in order to understand their function. The recent crystal structure of a doubly persulfided CsdA-CsdE complex was central to our proposal of a novel mechanism for the transfer of sulfur atoms across protein-protein interfaces and to deciphering the role of conserved Cys loop motifs present both in CsdA and in SufS.
The connection with tRNA biology is made through TcdA, the enzyme responsible for the synthesis of “cyclic t6A” (ct6A) in bacteria, protists, fungi and plants, where it ensures the fidelity and efficiency of translation. We have investigated the structure of TcdA both in free form and associated with tRNA using a combination of X-ray crystallography/SAXS and other techniques, which represents one first step toward deciphering the biological role of this intriguing enzyme.
Carbohydrate active and sugar metabolic enzymes
Carbohydrate active enzymes are enzymes capable of synthesising or breaking glycosidic bonds as well as the non-catalytic carbohydrate binding modules (CBMs) that frequently are associated with the active enzymes. Sugar metabolic enzyme is a wider term describing any enzyme which recognises, binds and modifies sugar molecules, usually within the context of a biochemical pathway. Carbohydrate active and sugar metabolic enzymes are also relevant enzymes for biotechnological applications, including the biofuel industry, as well as for the analysis of plant-fungi interactions owing to the widespread use of extracellular glycosyl hydrolases by plant pathogenic fungi.
Improving Methods for Production of Therapeutic Molecules
We are interested in the development and improvement of new technologies and production tools for complex protein biologics using yeast expression methodologies and other eukaryotic expression systems. Our group was a member of the FP7 Project ComplexINC, which conceptualised and systematically generated advanced toolkits to enable high-throughput assembly of complex biologics and metabolic pathways using eukaryotic expression systems. The ultimate goal of these toolkits, including two yeast-based toolkits developed in our laboratory, was enabling micro- and large-scale production of high-quality protein biologics for drug discovery and as biotherapeutics.
ComplexINC conceptualizes and systematically generates advanced toolkits to enable high-throughput assembly of complex biologics and metabolic pathways using eukaryotic expression systems. The ultimate goal of these toolkits, including two yeast-based toolkits developed in our laboratory, is enabling micro- and large-scale production of high-quality protein biologics for drug discovery and as biotherapeutics.