Green fluorescent proteins (GFP) and GFP-like proteins all undergo an autocatalytic post-translational modification to form a centrally located chromophore. Structural analyses of all the GFP and GFP-like proteins in the protein databank were undertaken to determine the role of the tight-turn, broken hydrogen bonding, Gly67, Glu222 and Arg96 in the biosynthesis of the imidazolone group from 65SYG67. The analysis was supplemented by computational generation of the conformation adopted by uncyclized wild-type GFP. The data analysis suggests that Arg96 interacts with the Tyr66 carbonyl, stabilizing the reduced enolate intermediate that is required for cyclization; the carboxylate of Glu222 acts as a base facilitating, through a network of two waters, the abstraction of a hydrogen from the α-carbon of Tyr66; a tight-turn conformation is required for autocatalytic cyclization. This conformation is responsible for a partial reduction in the hydrogen bonding network around the chromophore-forming region of the immature protein.
Lemay, N.P.; Morgan, A.L.; Archer, E.J.; Dickson, L.A.; Megley, C.M.; Zimmer, M. The role of the tight-turn, broken hydrogen bonding, Glu222 and Arg96 in the post-translational green fluorescent protein chromophore formation. Chem. Phys. 2008, 348, 152-160. http://dx.doi.org/10.1016/j.chemphys.2008.02.055.
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