Molybdo-enzymes: from catalysis to biogenesis. New insights from EPR spectroscopy

Title: Molybdo-enzymes: from catalysis to biogenesis. New insights from EPR spectroscopy

Speaker: Bruno Guigliarelli

Affiliation: 

Full Professor at Aix-Marseille Université

Laboratoire de Bioenergetique et d'Ingenierie des Protéines (BIP), CNRS Marseille

Abstract:

Mononuclear molybdo-enzymes are found in virtually all living organisms. In Prokaryotes, most of these enzymes harbour a large Mo-bis pyranopterin guanosine dinucleotide cofactor and catalyse a wide diversity of redox reactions involved in major biogeochemical cycles of nitrogen, sulfur, carbon. In spite of the similarity of their Mo-bisPGD cofactor, these enzymes are able to use a broad diversity of substrates, but the molecular factors which trigger their reactivity remain largely unknown. During catalysis, the molybdenum ion cycles between the +IV and +VI redox states, the intermediate Mo(V) state being EPR-active (S=1/2). Several Mo(V) species have been identified, but in spite of numerous crystallographic and spectroscopic studies, their structure and catalytic relevance is still strongly debated.

 As EPR is very sensitive to spin-spin interactions between close paramagnetic species (magnetic nuclei or other metal cofactors), such magnetic coupling can be analyzed by multifrequency continuous wave EPR or by the most advanced pulsed EPR techniques (HYSCORE, ENDOR, ELDOR-DEER) to give high resolution structural data in a wide range of distances (from few Å to several nm). We will present recent results on bacterial Mo-enzymes like nitrate reductases and formate dehydrogenases to illustrate how the combination of these EPR techniques with site-directed mutagenesis, selective isotope labeling and theoretical calculations provide an accurate view of the Mo-cofactor structure in the Mo(V) catalytic intermediates and enable to decipher biogenesis steps leading to active enzymes. 

About Bruno Guigliarelli:

Bruno Guigliarelli is Professor in Physics at Aix-Marseille University, heading the group of “Biophysics of Metalloproteins” (18 researchers) in the Laboratory of Bioenergetics and Protein Engineering (BIP-UMR7281). After studies in chemical-physics at ENS Cachan, he obtained his PhD in molecular spectroscopy from the University of Aix-Marseille I in 1986, and his Habilitation (HDR) in 1990. With his group, he develops for several years the applications of Electron Paramagnetic Resonance (EPR) to the structural and functional studies of complex enzymes and proteins.  His research activity concerns mainly oxidoreductases involved in the energy metabolisms of prokaryotes and their applications in health or bioenergy (hydrogenases, molybdo-enzymes). He has a longstanding expertise in the study of electronic, magnetic and structural properties of metal clusters, radical chemistry, catalytic mechanisms, electron and proton transfers, and protein-protein interactions. His multidisciplinary approach combine the use of advanced EPR techniques, electrochemistry, kinetics studies, theoretical modelling, with other physico-chemical approaches. He notably developed the biostructural applications of spin-labeling combined with EPR to investigate the dynamic properties and structural transitions in proteins and enzymes, and their role in physiological functions.

He has authored more than 160 publications (>5700 citations), 3 books, and supervised 12 PhD theses. He has been previously President of the French EPR Society (ARPE, 2007-11) and President of the French group of Magnetism and Magnetic Resonances (MRM-SCF/SFP, 2013-19), and he currently manages the Aix-Marseille EPR platform which is especially devoted to applications in Biology and Chemistry in the French EPR network INFRANALYTICS and in the European Research Infrastructure MOSBRI.