Crystal Structure of theAequorea victoriaGreen Fluorescent Protein

The green fluorescent protein (GFP) from the Pacific Northwest jellyfish Aequorea victoria has generated intense interest as a marker for gene expression and localization of gene products. The chromophore, resulting from the spontaneous cyclization and oxidation of the sequence -Ser 65 (or Thr 65 )-Tyr 66 -Gly 67 -, requires the native protein fold for both formation and fluorescence emission. The structure of Thr 65 GFP has been determined at 1.9 angstrom resolution. The protein fold consists of an 11-stranded β barrel with a coaxial helix, with the chromophore forming from the central helix. Directed mutagenesis of one residue adjacent to the chromophore, Thr 203 , to Tyr or His results in significantly red-shifted excitation and emission maxima.