Green Fluorescent Proteins (GFP) and GFP-like proteins all undergo an autocatalytic posttranslational 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 tightturn, 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 Glu 222 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.

No abstract

No abstract