Biophysical characterization of the interaction between SNH and QLQ protein domains

MARCO C. MIOTTO

La Plata

Congreso; XLVII Reunión Anual de la Sociedad Argentina de Biofísica; 2018

Plant development is a process that is finely regulated by the action of variousmolecular mechanisms. One of these mechanisms comprises the activation orrepression of the expression of certain genes, through the action of specificproteins. The Growth-Regulating Factors (GRF) ? GRF-Interacting Factors (GIF)system is formed by two families of activators and transcriptional coactivatorsconserved in terrestrial plants. A range of studies have demonstrated the functionof the combined action of these proteins on plant development, but there is nobiophysical evidence of such protein-protein interaction so far.Here we present the first biophysical approach to unveil Arabidopsis thaliana GRFand GIF protein interaction at a structural level. Since the proteins show a highdegree of intrinsic disorder throughout the sequence, we designed proteinconstructs with the regions genetically mapped as essential for the interactionbetween GRF and GIF, the QLQ and SNH domains, respectively. We characterizedthe isolated constructs and their complexes using circular dichroism, fluorescenceand nuclear magnetic resonance spectroscopies. The SNH domain adopts unstablehelical conformations, that are stabilized upon compex formation. NMRparamagnetic relaxation enhancement shows that SNH forms two parallel helicesin the complex. The QLQ:SNH complex stoichiometries are variable and depend onthe partners involved. Altogether our data puts forward an unexpected level ofcomplexity in this interaction network.