Ultrafast anisotropic protein quake propagation after CO photodissociation in myoglobin.
"Protein quake" denotes the dissipation of excess energy across a protein, in response to a local perturbation such as the breaking of a chemical bond or the absorption of a photon. Femtosecond time-resolved small- and wide-angle X-ray scattering (TR-SWAXS) is capable of tracking such ultrafast protein dynamics. However, because the structural interpretation of the experiments is complicated, a molecular picture of protein quakes has remained elusive. In addition, new questions arose from recent TR-SWAXS data that were interpreted as underdamped oscillations of an entire protein, thus challenging the long-standing concept of overdamped global protein dynamics. Based on molecular-dynamics simulations, we present a detailed molecular movie of the protein quake after carbon monoxide (CO) photodissociation in myoglobin. The simulations suggest that the protein quake is characterized by a single pressure peak that propagates anisotropically within 500 fs across the protein and further into the solvent. By computing TR-SWAXS patterns from the simulations, we could interpret features in the reciprocal-space SWAXS signals as specific real-space dynamics, such as CO displacement and pressure wave propagation. Remarkably, we found that the small-angle data primarily detect modulations of the solvent density but not oscillations of the bare protein, thereby reconciling recent TR-SWAXS experiments with the notion of overdamped global protein dynamics.
Institute for Microbiology and Genetics, Georg-August University Göttingen, 37077 Goettingen, Germany; Göttingen Center for Molecular Biosciences, Georg-August University Göttingen, 37077 Goettingen, Germany.
Levin U L
LU
Brinkmann
Institute for Microbiology and Genetics, Georg-August University Göttingen, 37077 Goettingen, Germany; Göttingen Center for Molecular Biosciences, Georg-August University Göttingen, 37077 Goettingen, Germany jhub@gwdg.de.
Jochen S
0000-0001-7716-1767
JS
Hub
D000818:Animals; D016880:Anisotropy; D002248:Carbon Monoxide / Q000737:chemistry*; D006736:Horses; D008962:Models, Theoretical; D056004:Molecular Dynamics Simulation; D009211:Myoglobin / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D053838:Scattering, Small Angle; D012997:Solvents / Q000737:chemistry; D013816:Thermodynamics
D009211:Myoglobin; D012997:Solvents; D002248:Carbon Monoxide
free-electron laser; molecular dynamics; time-resolved SAXS/WAXS