The 2.1 Å Crystal Structure of copGFP, a Representative Member of the Copepod Clade Within the Green Fluorescent Protein Superfamily

• Published in: Journal of molecular biology Vol. 359; no. 4; pp. 890 - 900
• Main Authors: Wilmann, Pascal G., Battad, Jion, Petersen, Jan, Wilce, Matthew C.J., Dove, Sophie, Devenish, Rodney J., Prescott, Mark, Rossjohn, Jamie
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.06.2006
• Subjects: copepoda protein; copGFP; GFP structure; protein fluorescence; copepoda protein; CPs; FPs; QY; vdw; GFP structure; GFP; protein fluorescence; ppluGFP2; BSA; copGFP; r.m.s.d; FRET
• DOI: 10.1016/j.jmb.2006.04.002
• ISSN: 0022-2836

The green fluorescent protein (avGFP), its variants, and the closely related GFP-like proteins are characterized structurally by a cyclic tri-peptide chromophore located centrally within a conserved β-can fold. Traditionally, these GFP family members have been isolated from the Cnidaria although recently, distantly related GFP-like proteins from the Bilateria, a sister group of the Cnidaria have been described, although no representative structure from this phylum has been reported to date. We have determined to 2.1 Å resolution the crystal structure of copGFP, a representative GFP-like protein from a copepod, a member of the Bilateria. The structure of copGFP revealed that, despite sharing only 19% sequence identity with GFP, the tri-peptide chromophore (Gly57-Tyr58-Gly59) of copGFP adopted a cis coplanar conformation within the conserved β-can fold. However, the immediate environment surrounding the chromophore of copGFP was markedly atypical when compared to other members of the GFP-superfamily, with a large network of bulky residues observed to surround the chromophore. Arg87 and Glu222 (GFP numbering 96 and 222), the only two residues conserved between copGFP, GFP and GFP-like proteins are involved in autocatalytic genesis of the chromophore. Accordingly, the copGFP structure provides an alternative platform for the development of a new suite of fluorescent protein tools. Moreover, the structure suggests that the autocatalytic genesis of the chromophore is remarkably tolerant to a high degree of sequence and structural variation within the β-can fold of the GFP superfamily.