The 2.1A crystal structure of the far-red fluorescent protein HcRed: inherent conformational flexibility of the chromophore.
We have determined the crystal structure of HcRed, a far-red fluorescent protein isolated from Heteractis crispa, to 2.1A resolution. HcRed was observed to form a dimer, in contrast to the monomeric form of green fluorescent protein (GFP) or the tetrameric forms of the GFP-like proteins (eqFP611, Rtms5 and DsRed). Unlike the well-defined chromophore conformation observed in GFP and the GFP-like proteins, the HcRed chromophore was observed to be considerably mobile. Within the HcRed structure, the cyclic tripeptide chromophore, Glu(64)-Tyr(65)-Gly(66), was observed to adopt both a cis coplanar and a trans non-coplanar conformation. As a result of these two conformations, the hydroxyphenyl moiety of the chromophore makes distinct interactions within the interior of the beta-can. These data together with a quantum chemical model of the chromophore, suggest the cis coplanar conformation to be consistent with the fluorescent properties of HcRed, and the trans non-coplanar conformation to be consistent with non-fluorescent properties of hcCP, the chromoprotein parent of HcRed. Moreover, within the GFP-like family, it appears that where conformational freedom is permissible then flexibility in the chromophore conformation is possible.
Wilmann
Pascal G
PG
The Protein Crystallography Unit, Monash Centre for Synchrotron Science, School of Biomedical Sciences, Monash University, Clayton, Vic. 3800, Australia.
Petersen
Jan
J
Pettikiriarachchi
Anne
A
Buckle
Ashley M
AM
Smith
Sean C
SC
Olsen
Seth
S
Perugini
Matthew A
MA
Devenish
Rodney J
RJ
Prescott
Mark
M
Rossjohn
Jamie
J
D000818:Animals; D008164:Luminescent Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012615:Sea Anemones / Q000235:genetics / Q000378:metabolism*; D040681:Structural Homology, Protein; D000097573:Red Fluorescent Protein
D008164:Luminescent Proteins; D000097573:Red Fluorescent Protein