The 2.1A crystal structure of the far-red fluorescent protein HcRed: inherent conformational flexibility of the chromophore |
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Authors: | Wilmann Pascal G Petersen Jan Pettikiriarachchi Anne Buckle Ashley M Smith Sean C Olsen Seth Perugini Matthew A Devenish Rodney J Prescott Mark Rossjohn Jamie |
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Institution: | The Protein Crystallography Unit, Monash Centre for Synchrotron Science, School of Biomedical Sciences, Monash University, Clayton, Vic. 3800, Australia. |
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Abstract: | 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. |
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Keywords: | HcRed fluorescent protein structure chromophore configuration |
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