Figure 3.
Fig. 3. The proposed conjugation-trapping mechanism for GFP
chromophore formation. The chemical mechanism for GFP
chromophore formation (Left) is displayed along with a cartoon
representation of the corresponding reaction coordinate (Right).
The reaction coordinates (x axis) for GFP (green) and a
canonical -helix (red) are
displayed against increasing energy for the chromophore residues
(y axis), to highlight the three features favoring ring
synthesis in the GFP scaffold: architectural distortions, R96
enhancement of the G67 nucleophile, and E222 stabilization of
the dehydration transition state. (a) Peptide cyclization to
generate a destabilized intermediate. (b) Dehydration, initiated
by the T62 carbonyl, to trap the cyclized product through
conjugation. (c) Oxidation to generate an aromatic imidazolone
and conjugate the two ring systems. The chromophore images
superimposed onto the cartoon are (from left to right) the R96A
precyclization structure, model of cyclized intermediate, model
of reduced intermediate and the R96A mature chromophore
structure. Our data do not address the oxidation transition
state (displayed as dashed lines).
-helix (red) are
displayed against increasing energy for the chromophore residues
(y axis), to highlight the three features favoring ring
synthesis in the GFP scaffold: architectural distortions, R96
enhancement of the G67 nucleophile, and E222 stabilization of
the dehydration transition state. (a) Peptide cyclization to
generate a destabilized intermediate. (b) Dehydration, initiated
by the T62 carbonyl, to trap the cyclized product through
conjugation. (c) Oxidation to generate an aromatic imidazolone
and conjugate the two ring systems. The chromophore images
superimposed onto the cartoon are (from left to right) the R96A
precyclization structure, model of cyclized intermediate, model
of reduced intermediate and the R96A mature chromophore
structure. Our data do not address the oxidation transition
state (displayed as dashed lines).