6pfs
From Proteopedia
rsEGFP2 with a chlorinated chromophore in the fluorescent on-state in a contracted unit cell
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 PubMedDouble-bond photoisomerization in molecules such as the green fluorescent protein (GFP) chromophore can occur either via a volume-demanding one-bond-flip pathway or via a volume-conserving hula-twist pathway. Understanding the factors that determine the pathway of photoisomerization would inform the rational design of photoswitchable GFPs as improved tools for super-resolution microscopy. In this communication, we reveal the photoisomerization pathway of a photoswitchable GFP, rsEGFP2, by solving crystal structures of cis and trans rsEGFP2 containing a monochlorinated chromophore. The position of the chlorine substituent in the trans state breaks the symmetry of the phenolate ring of the chromophore and allows us to distinguish the two pathways. Surprisingly, we find that the pathway depends on the arrangement of protein monomers within the crystal lattice: in a looser packing, the one-bond-flip occurs, whereas, in a tighter packing (7% smaller unit cell size), the hula-twist occurs. Structural Evidence of Photoisomerization Pathways in Fluorescent Proteins.,Chang J, Romei MG, Boxer SG J Am Chem Soc. 2019 Oct 2;141(39):15504-15508. doi: 10.1021/jacs.9b08356. Epub, 2019 Sep 24. PMID:31533429[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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