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Spectral and Structural Comparison Between Bright and Dim Green Fluorescent Proteins in Amphioxus

The cephalochordate Amphioxus naturally co-expresses fluorescent proteins (FPs) with different brightness, which thus offers the rare opportunity to identify FP molecular feature/s that are associated with greater/lower intensity of fluorescence. Here, we describe the spectral and structural characteristics of green FP (bfloGFPa1) with perfect (100 %) quantum efficiency yielding to unprecedentedly-high brightness, and compare them to those of co-expressed bfloGFPc1 showing extremely-dim brightness due to low (0.1 %) quantum efficiency. This direct comparison of structure-function relationship indicated that in the bright bfloGFPa1, a Tyrosine (Tyr159) promotes a ring flipping of a Tryptophan (Trp157) that in turn allows a cis-trans transformation of a Proline (Pro55). Consequently, the FP chromophore is pushed up, which comes with a slight tilt and increased stability. FPs are continuously engineered for improved biochemical and/or photonic properties, and this study provides new insight to the challenge of establishing a clear mechanistic understanding between chromophore structural environment and brightness level.


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Bomati EK, Haley JE, Noel JP, and Deheyn DD:
Spectral and structural comparison between bright and dim green fluorescent proteins in Amphioxus

Scientific Reports 4: 5469 (2014); doi: 10.1038/srep05469