title: GFP's mechanical intermediate states.
abstract: Green fluorescent protein (GFP) mutants have become the most widely used fluorescence markers in the life sciences, and although they are becoming increasingly popular as mechanical force or strain probes, there is little direct information on how their fluorescence changes when mechanically stretched. Here we derive high-resolution structural models of the mechanical intermediate states of stretched GFP using steered molecular dynamics (SMD) simulations. These structures were used to produce mutants of EGFP and EYFP that mimic GFP's different mechanical intermediates. A spectroscopic analysis revealed that a population of EGFP molecules with a missing N-terminal α-helix was significantly dimmed, while the fluorescence lifetime characteristic of the anionic chromophore state remained unaffected. This suggests a mechanism how N-terminal deletions can switch the protonation state of the chromophore, and how the fluorescence of GFP molecules in response to mechanical disturbance might be turned off.
authors.affiliation: Laboratory of Applied Mechanobiology, Department of Health Sciences and Technology, ETH Zürich, Zürich, Switzerland.
authors.forename: John
authors.initials: J
authors.lastname: Saeger
authors.forename: Vesa P
authors.initials: VP
authors.lastname: Hytönen
authors.forename: Enrico
authors.initials: E
authors.lastname: Klotzsch
authors.forename: Viola
authors.initials: V
authors.lastname: Vogel
mesh_terms: D018360:Crystallography, X-Ray; D005453:Fluorescence; D049452:Green Fluorescent Proteins / Q000737:chemistry / Q000235:genetics; D006860:Hydrogen Bonding; D007700:Kinetics; D008027:Light; D055595:Mechanical Phenomena; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D011487:Protein Conformation; D013057:Spectrum Analysis
chemical_list: D049452:Green Fluorescent Proteins