5oxb
Structure of blue-light irradiated Cerulean
Structural highlights
FunctionGFP_AEQVI Energy-transfer acceptor. Its role is to transduce the blue chemiluminescence of the protein aequorin into green fluorescent light by energy transfer. Fluoresces in vivo upon receiving energy from the Ca(2+)-activated photoprotein aequorin. Publication Abstract from PubMedECFP, the first usable cyan fluorescent protein (CFP), was obtained by adapting the tyrosine-based chromophore environment in green fluorescent protein to that of a tryptophan-based one. This first-generation CFP was superseded by the popular Cerulean, CyPet, and SCFP3A that were engineered by rational and random mutagenesis, yet the latter CFPs still exhibit suboptimal properties of pH sensitivity and reversible photobleaching behavior. These flaws were serendipitously corrected in the third-generation CFP mTurquoise and its successors without an obvious rationale. We show here that the evolution process had unexpectedly remodeled the chromophore environment in second-generation CFPs so they would accommodate a different isomer, whose formation is favored by acidic pH or light irradiation and which emits fluorescence much less efficiently. Our results illustrate how fluorescent protein engineering based solely on fluorescence efficiency optimization may affect other photophysical or physicochemical parameters and provide novel insights into the rational evolution of fluorescent proteins with a tryptophan-based chromophore. Chromophore Isomer Stabilization Is Critical to the Efficient Fluorescence of Cyan Fluorescent Proteins.,Gotthard G, von Stetten D, Clavel D, Noirclerc-Savoye M, Royant A Biochemistry. 2017 Nov 27. pii: 10.1021/acs.biochem.7b01088. doi:, 10.1021/acs.biochem.7b01088. PMID:29148725[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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