Ultrafast myoglobin structural dynamics observed with an X-ray free-electron laser.

Matteo Levantino,Diling Zhu,Marco Cammarata,James Michael Glownia,Antonio Cupane,Hyotcherl Ihee,Giorgio Schirò,Grazia Cottone,Henrik Till Lemke,Mathieu Chollet

doi:10.1038/ncomms7772

Abstract

Light absorption can trigger biologically relevant protein conformational changes. The light-induced structural rearrangement at the level of a photoexcited chromophore is known to occur in the femtosecond timescale and is expected to propagate through the protein as a quake-like intramolecular motion. Here we report direct experimental evidence of such ‘proteinquake’ observed in myoglobin through femtosecond X-ray solution scattering measurements performed at the Linac Coherent Light Source X-ray free-electron laser. An ultrafast increase of myoglobin radius of gyration occurs within 1 picosecond and is followed by a delayed protein expansion. As the system approaches equilibrium it undergoes damped oscillations with a ~3.6-picosecond time period. Our results unambiguously show how initially localized chemical changes can propagate at the level of the global protein conformation in the picosecond timescale.

Highlights

Light absorption can trigger biologically relevant protein conformational changes
The analysis of the elastic response of the protein to the active site rearrangement is complicated by the simultaneous dissipation of the excess energy that is deposited by the photolysis pulse on the haem chromophore
These authors have used time-resolved X-ray solution scattering, an experimental technique able to track the structural dynamics of proteins in solution[30], to show that the backbone carbon atoms of the protein helices increase their distance from the interior of the photoreaction centre on a picosecond timescale

Summary

Introduction

Light absorption can trigger biologically relevant protein conformational changes. The lightinduced structural rearrangement at the level of a photoexcited chromophore is known to occur in the femtosecond timescale and is expected to propagate through the protein as a quake-like intramolecular motion. These authors have used time-resolved X-ray solution scattering, an experimental technique able to track the structural dynamics of proteins in solution[30], to show that the backbone carbon atoms of the protein helices increase their distance from the interior of the photoreaction centre on a picosecond timescale.

Results

Conclusion