The photoreceptor protein of Euglena gracilis

Abstract

We isolated the photoactive protein Erh, isolated from the photoreceptor of the unicellular photosynthetic flagellate Euglena gracilis. It is a 27 kDa protein with a photocycle resembling that of sensory rhodopsin, but with at least one stable intermediate. We recorded the absorption spectrum of the parent form of this protein both under native form and in the presence of hydroxylamine and sodium borohydride, and the fluorescence spectra of both the parent and intermediate forms.We suggest that Erh is a rhodopsin-like protein and propose a simple photocycle. This protein shows optical bistability, without thermal deactivation. ß

Algae through the looking glass

“…The results of these measurements highlight the photochromic behavior of the photoreceptor of Euglena , and state that its photoreceptive proteins possess strong spectroscopic similarities with rhodopsin‐like proteins (Barsanti, Evangelista, Passarelli, Frassanito, & Gualtieri, ; Barsanti, Passarelli, Walne, & Gualtieri, ; Mercatelli et al, ).…”

In Vivo Absorption Spectra of the Two Stable States of the Euglena Photoreceptor Photocycle

“…Barsanti et al. (10) isolated a photoactive protein from the photoreceptor of Euglena with an absorption maximum at 515 nm, and a spectroscopic behavior similar to that of the photoreceptor. They also extracted retinal from a photoreceptor preparation (11).…”

A rhodopsin-like protein in Cyanophora paradoxa: gene sequence and protein immunolocalization

“…As far as algae are concerned, the earlier predictions based on photobiology and biochemistry are in many cases corroborated by contemporary genomic data on Type I rhodopsin sequences in different taxa [13,14]. Spectroscopical and biochemical evidence of rhodopsin-based photoreceptor is available for algae belonging to Euglenophyta [15][16][17] and Heterokontophyta [18,19]. Genes encoding functional protein probably related to photoreception have been detected both in prokaryotic (Cyanophyta) [20] and eukaryotic genera (Dinophyta, Cryptophyta, Chlorophyta) [21][22][23][24], though examples of transporters (proton or chloride transport) are also present [25].…”

“…cDNA was synthesized from oligo (dT) [12][13][14][15][16][17][18] primers (Invitrogen, USA) and 2 lg of total RNA in reverse transcription PCR, using SuperScript TM II RNase H-RT (Invitrogen) according to the manufacturer's suggested protocol.…”