ORAL COMMUNICATION: Paramagnetic resonance enhancement as a tool to probe low populated species in highly dinamyc protein systems

CARLOS W. BERTONCINI

Rosario

Workshop; Taller Fronteras en Resonancia Magnetica: de los Materiales a los Sistemas Biológicos; 2013

Sistema Nacional de Resonancia Magnética

PARAMAGNETIC RESONANCE ENHANCEMENT AS A TOOL TO PROBE LOW POPULATED SPECIES IN HIGHLY DINAMYC PROTEIN SYSTEMSCarlos W. Bertoncini, Santiago Estaban-Martín, Jordi Sylvestre-Ryan & XavierSalvatellaInstitute for Research in Biomedicine, Barcelona, Spain & Barcelona SupercomputingCenter, Barcelona, Spain. email: carlos.bertoncini@irbbarcelona.orgKeywords: NMR, Structure Calculation, Protein Dynamics, Intrinsically DisorderedProteins, Protein Folding.In the last decade it has become evident that dynamic states of proteins playimportant physiological and pathological roles. Disordered states of proteins embody one extreme example of such relevant protein dynamics. It has been shown that transient low populated states are often present in these systems and can play an active role in their biological activity. The structural characterization of such states has so far largely relied on ensemble representations, which in principle account for both their local and global structural features. However, these approaches are inherently of low resolution due to the large number of degrees of freedom of conformationalensembles, and to the sparse nature of the experimental data used to determine them.We have developed an NMR-based experimental and computational framework toovercome these limitations by the use of extensive sets of nitroxide spin labels on these proteins. Spin labels cause paramagnetic-induced relaxation enhancement(PRE) on nuclei resonances, an effect that is modulated by the distance to the spin label (r-6). Computational studies on synthetic data show that, contrary to ensemble interpretations of PRE data, tertiary interactions in disordered states of proteins can be mapped at high resolution by fitting PRE data to a rather small number of conformations, which can be as low as one. As examples of this application we characterized low populated species present in the acid-unfolded state of apomyoglobin and in the intrinsically disordered state of alpha-synuclein from experimentally measured PRE data.These result open up the possibility of determining the topology of cooperatively collapsed and hidden folded states when these are present in the vast conformational landscape accessible to disordered states of proteins.