title: Photoactivation Reduces Side-Chain Dynamics of a LOV Photoreceptor.
abstract: 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.
authors.affiliation: Jülich Centre for Neutron Science (JCNS) and Institute for Complex Systems (ICS), Forschungszentrum Jülich, Jülich, Germany. Electronic address: a.stadler@fz-juelich.de.
authors.forename: Andreas M
authors.initials: AM
authors.lastname: Stadler
authors.affiliation: Institute of Molecular Enzyme Technology, Heinrich-Heine-Universität Düsseldorf, Forschungszentrum Jülich, Jülich, Germany.
authors.forename: Esther
authors.initials: E
authors.lastname: Knieps-Grünhagen
authors.affiliation: Chair of Biotechnology, RWTH Aachen University, Aachen, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Bocola
authors.affiliation: Heinz Maier-Leibnitz Zentrum, Technische Universität München, Garching, Germany.
authors.forename: Wiebke
authors.initials: W
authors.lastname: Lohstroh
authors.affiliation: Jülich Centre for Neutron Science (JCNS), Outstation at MLZ, Forschungszentrum Jülich, Garching, Germany.
authors.forename: Michaela
authors.initials: M
authors.lastname: Zamponi
authors.affiliation: Institute of Molecular Enzyme Technology, Heinrich-Heine-Universität Düsseldorf, Forschungszentrum Jülich, Jülich, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Krauss
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry; D017666:Deuterium Oxide; D004058:Diffusion; D004548:Elasticity; D019277:Entropy; D008027:Light; D056004:Molecular Dynamics Simulation; D009502:Neutrons; D020283:Photoreceptors, Microbial / Q000737:chemistry*; D016958:Pseudomonas putida / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D020283:Photoreceptors, Microbial; D017666:Deuterium Oxide