Structural analysis of the immature form of the GFP homologue DsRed

The crystal structures of DsRed have shown that it contains an unusual non-proline containing cis peptide linkage. We have shown that it is also present in the precyclized immature form of DsRed, thereby eliminating the possibility that cis/trans isomerization drives the formation of the acylimine, which is responsible for DsRedʹs red fluorescence. Two mechanisms have been proposed for chromophore formation in green fluorescent protein (GFP), a ‘reduced’ and an ‘oxidized’ mechanism. DsRed adopts a tight turn conformation, such as that found in GFP, in the immature intermediate proposed in the oxidized mechanism, but not in the one predicted by the reduced mechanism.