Directionality of dipoles of fluoregen cofactors in context of crystal structure

J. Brynda, J. Myšková and J. Lazar

Ústav organické chemie a biochemie AV ČR, v. v. i., Flemingovo náměstí 542/2, 166 10 Praha 6, Česká Republika

brynda@uochb.cas.cz

The popularity of fluorescent proteins comes from their endogenous cofactor¹, which is formed spontaneously when the backbone of three amino acid residues (Ser−Tyr−Gly in the green fluorescent protein) cyclizes and dehydrates^2,3.  The following oxidation step extends the aromatic system of the nascent chromophore, which, upon illumination, exhibits intense fluorescence. The chromophore interacts strongly with neighboring residues within the 11-stranded β-barrel. Perturbation of the immediate environment through mutagenesis of key residues results in protein variants with altered spectroscopic and chemical properties⁴. Crystals of fluorescent proteins provide a suitable system for determining directional optical properties of the corresponding fluorophores. However, knowledge of the orientation of fluorescent protein molecules within the crystal is a crucial prerequisite.

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