Intramolecular photo-switching and intermolecular energy transfer as primary photoevents in photoreceptive processes: The case of Euglena gracilis

Year: 2009

Authors: Mercatelli R., Quercioli F., Barsanti L., Evangelista V., Coltelli P., Passarelli V., Frassanito A.M., Gualtieri P.

Autors Affiliation: Istituto Sistemi Complessi, CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy;
Istituto di Biofisica, CNR, Via Moruzzi 1, 56124 Pisa, Italy;
ISTI, CNR, Via Moruzzi 1, 56124 Pisa, Italy

Abstract: In this paper we report the results of measurements performed by FLIM on the photoreceptor of Euglena gracilis. This organelle consists of optically bistable proteins, characterized by two thermally stable isomeric forms: A498, non fluorescent and B462, fluorescent.
Our data indicate that the primary photoevent of Euglena photoreception upon photon absorption consists of two contemporaneous different phenomena: an intramolecular photo-switch (i.e., A498 becomes B462), and a intermolecular and unidirectional Forster-type energy transfer. During the FRET process, the fluorescent B462 form acts as donor for the non-fluorescent A498 form of the protein nearby, which acts as acceptor. We hypothesize that in nature these phenomena follow each other with a domino progression along the orderly organized and closely packed proteins in the photoreceptor layer(s), modulating the isomeric composition of the photoreceptive protein pool. This mechanism guarantees that few photons are sufficient to produce a signal detectable by the cell.

Journal/Review: BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS

Volume: 385 (2)      Pages from: 176  to: 180

KeyWords: Algal protein; Rhodopsin like protein; Unclassified drug, article; Bioprocess; Biotransformation; Cell organelle; Confocal microscopy; Energy transfer; Euglena gracilis; Fluorescence imaging; Fluorescence resonance energy transfer; Isomer; Light absorption; Molecular interaction; Multiphoton microscopy; Nonhuman; Photodynamics; Photon; Photoswitching; Priority journal; Protein interaction; Signal detection; Thermostability, Animals; Euglena gracilis; Fluorescence Resonance Energy Transfer; Photoreceptor Cells, Invertebrate, Euglena; Euglena gracilis
DOI: 10.1016/j.bbrc.2009.05.034

Citations: 6
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