To Örebro University

The dimeric UVR8 protein is a ultraviolet-B radiation (280-315 nm) photoreceptor responsible for the first step in UV-B regulation of gene expression in plants. Its action comprises the actual absorption of the UV quanta by a tryptophan array at the protein-protein interface, followed by monomerisation, and subsequent aggregation with downstream signaling components. A crystal structure of the Arabidopsis thaliana tryptophan-rich wild type UVR8 protein dimer was recently published, showing the presence of several salt bridges involving arginines R146, R286, R338 and R354. In this work, molecular dynamics simulations in conjunction with umbrella sampling was used to calculate the binding free energy for the wild type UVR8 dimer and three of its mutants (R286A, R338A and R286A/R338A), in order to verify whether the key mutants are able to disrupt the dimeric structure as indicated experimentally.