The chromophore environment of mTFP1, amFP486 and avGFP-S65T. (A) The chromophore of mTFP1 (Protein data bank (PDB) code 2HQK) in space filling representation . The side chains of residues that are discussed in the text and that are in close proximity to the chromophore are shown in ball-and-stick. Hydrogen bonds are indicated with black dotted lines. Cα for each residue is represented as a black sphere. Atoms labeled 'W' are ordered water molecules. (B) The chromophore environment of amFP486 showing the residues that are structurally aligned with the residues represented in (A) (PDB code 2A46) . (C) The chromophore environment of avGFP-S65T (and EGFP) showing the residues that structurally align with those represented in (A) (PDB code 1EMA) . avGFP-S65T and EGFP differ only by the Phe64Leu mutation which does not significantly modify the conformation of any residues shown in this figure.