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 PubMedGreen fluorescent protein (GFP) is widely utilized as a fluorescent tag in biochemical fields. Whereas the intermediate (I) state has been proposed in the photoreaction cycle in addition to the A and B states, until now the structure of I has only been estimated by computational studies. In this paper, we report the crystal structures of the I stabilizing variants of GFP at high resolutions where respective atoms can be observed separately. Comparison with the structures in the other states highlights the structural feature of the I state. The side chain of one of the substituted residues, Val203, adopts the gauche- conformation observed for Thr203 in the A state, which is different from the B state. On the other hand, His148 interacts with the chromophore by ordinary hydrogen bonding with a distance of 2.85 A, while the weaker interaction by longer distances is observed in the A state. Therefore, it was indicated that it is possible to distinguish three states A, B and I by the two hydrogen bond distances Ogamma-Thr203...Oeta-chromophore and Ndelta1-His148...Oeta-chromophore. We discuss the characteristics of the I intermediate of wild-type GFP on the bases of the structure estimated from the variant structures by quantum chemical calculations. Structural characterization of green fluorescent protein in the I-state.,Takeda R, Tsutsumi E, Okatsu K, Fukai S, Takeda K Sci Rep. 2024 Oct 1;14(1):22832. doi: 10.1038/s41598-024-73696-y. PMID:39353998[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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