This title appears in the Scientific Report : 2016 

Photoactivation Reduces Side-Chain Dynamics of a LOV Photoreceptor
Stadler, Andreas (Corresponding author)
Knieps-Grünhagen, Esther / Bocola, Marco / Lohstroh, Wiebke / Zamponi, Michaela / Krauss, Ulrich
Neutronenstreuung ; ICS-1
Institut für Molekulare Enzymtechnologie (HHUD); IMET
Neutronenstreuung ; Neutronenstreuung; JCNS-1
Biophysical journal, 110 (2016) 5, S. 1064 - 1074
Cambridge, Mass. Cell Press 2016
Journal Article
Soft Matter, Health and Life Sciences
Jülich Centre for Neutron Research (JCNS)
Functional Macromolecules and Complexes
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We used neutron-scattering experiments to probe the conformational dynamics of the light, oxygen, voltage (LOV) photoreceptor PpSB1-LOV from Pseudomonas putida in both the dark and light states. Global protein diffusion and internal macromolecular dynamics were measured using incoherent neutron time-of-flight and backscattering spectroscopy on the picosecond to nanosecond timescales. Global protein diffusion of PpSB1-LOV is not influenced by photoactivation. Observation-time-dependent global diffusion coefficients were found, which converge on the nanosecond timescale toward diffusion coefficients determined by dynamic light scattering. Mean-square displacements of localized internal motions and effective force constants, <k′>, describing the resilience of the proteins were determined on the respective timescales. Photoactivation significantly modifies the flexibility and the resilience of PpSB1-LOV. On the fast, picosecond timescale, small changes in the mean-square displacement and <k′> are observed, which are enhanced on the slower, nanosecond timescale. Photoactivation results in a slightly larger resilience of the photoreceptor on the fast, picosecond timescale, whereas in the nanosecond range, a significantly less resilient structure of the light-state protein is observed. For a residue-resolved interpretation of the experimental neutron-scattering data, we analyzed molecular dynamics simulations of the PpSB1-LOV X-ray structure. Based on these data, it is tempting to speculate that light-induced changes in the protein result in altered side-chain mobility mostly for residues on the protruding Jα helix and on the LOV-LOV dimer interface. Our results provide strong experimental evidence that side-chain dynamics play a crucial role in photoactivation and signaling of PpSB1-LOV via modulation of conformational entropy.