Does Similar 3D structures Mean Similar Folding Pathway? Exploring the Conformational Folding Landscape of AVR Effectors from Phytopathogenic Fungi with High-Pressure NMR.

Cécile Dubois 1, Karine de Guillen1, Léa Mammri 1, Philippe Barthe 1, André Padilla1, Christian Roumestand 1.

Centre de Biochimie Structurale, UMR UM / 5048 CNRS / 1054 CNRS, Montpellier

Effectors are virulence factors consisting in sequence-unrelated small proteins secreted by pathogenic microorganisms during infection. The NMR or crystal 3D structures of several  effectors from the rice blast fungus Magnaporthe oryzae have been recently solved, including those of AVR-Pia and AVR-Pib [1,2]. Despite a lack of sequence similarity, both proteins have very similar β-sandwich structures. Structural convergence of proteins with poor sequence identity is rather common, probably due to the great sequence diversity of proteins, associated to a limited 3D structure accessible repertoire. Is this structural similarity associated to a similar folding pathway? This is the question we tackle in the present study. To this aim, we have analyzed the high-pressure unfolding of AVR-Pia and AVR-Pib with high-pressure NMR. We have designed a new approach to analyze the HP NMR data, based on distance-geometry calculations, that provides a meaningful description of the protein conformational folding landscape. As a result, a comparison of the folding pathways of AVR-Pia and AVR-Pib will be presented.

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