Rhodopsin: A Photopigment for Phototaxis in <i>Euglena gracilis</i>

Walne, Patricia L.; Passarelli, Vincenzo; Barsanti, Laura; Gualtieri, Paolo

doi:10.1080/07352689891304267

Cited by 16 publications

(7 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In fact carotenoids, especially in the form of rhodopsins (Walne et al 1998), have been found to be involved in photoorientation in many organisms such as Chlamydomonas, Halobacterium or Paramecium (Nakaoka et al 1991;Govorunova et al 2004;Kim et al 2009). Gualtieri and others, based on theoretical considerations, absorption spectroscopy and gas chromatography-mass spectrometry, proposed that the photoreceptor pigment for Euglena phototaxis is a rhodopsin (James et al 1992;Barsanti et al 1993a;Gualtieri 2001).…”

Section: Earlier Results and Hypothesesmentioning

confidence: 98%

Photomovement in Euglena

Häder

Iseki

2017

Advances in Experimental Medicine and Biology

View full text Add to dashboard Cite

Motile microorganisms such as the green Euglena gracilis use a number of external stimuli to orient in their environment. They respond to light with photophobic responses, photokinesis and phototaxis, all of which can result in accumulations of the organisms in suitable habitats. The light responses operate synergistically with gravitaxis, aerotaxis and other responses. Originally the microscopically obvious stigma was thought to be the photoreceptor, but later the paraxonemal body (PAB, paraflagellar body) has been identified as the light responsive organelle, located in the trailing flagellum inside the reservoir. The stigma can aid in light direction perception by shading the PAB periodically when the cell rotates helically in lateral light, but stigmaless mutants can also orient with respect to the light direction, and negative phototaxis does not need the presence of the stigma. The PAB is composed of dichroically oriented chromoproteins which is reflected in a pronounced polarotaxis in polarized light. There was a long debate about the potential photoreceptor molecule in Euglena, including carotenoids, flavins and rhodopsins. This discussion was terminated by the unambiguous proof that the photoreceptor is a 400 kDa photoactivated adenylyl cyclase (PAC) which consists of two α- and two β-subunits each. Each subunit possesses two BLUF (Blue Light receptor Using FAD) domains binding FAD, which harvest the light energy, and two adenylyl cyclases, which produce cAMP from ATP. The cAMP has been found to activate one of the five protein kinase s found in Euglena (PK.4). This enzyme in turn is thought to phosphorylate proteins inside the flagellum which result in a change in the flagellar beating pattern and thus a course correction of the cell. The involvements of PAC and protein kinase have been confirmed by RNA interference (RNAi). PAC is responsible for step-up photophobic responses as well as positive and negative phototaxis, but not for the step-down photophobic response, even though the action spectrum of this resembles those for the other two responses. Analysis of several colorless Euglena mutants and the closely related Euglena longa (formerly Astasia longa) confirms the results. Photokinesis shows a completely different action spectrum. Some other Euglena species, such as E. sanguinea and the gliding E. mutabilis, have been investigated, again showing totally different action spectra for phototaxis and photokinesis as well as step-up and step-down photophobic responses.

show abstract

Section: Earlier Results and Hypothesesmentioning

confidence: 98%

Photomovement in Euglena

Häder

Iseki

2017

Advances in Experimental Medicine and Biology

View full text Add to dashboard Cite

show abstract

“…The structure of the photoreceptor can be defined as a super lattice made up of closely stacked protein‐membrane lamellae separated by an aqueous phase. Each lamella is an ordered condensed phase complex of light‐sensory proteins (2). In general, as the cell rotates while swimming, the eyespot comes between the light source and the photoreceptor, thus modulating the light that reaches it, and regulating the steering of the locomotory flagellum.…”

Section: Introductionmentioning

confidence: 99%

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

Barsanti

Coltelli

Evangelista

et al. 2009

Photochem & Photobiology

Self Cite

View full text Add to dashboard Cite

Euglena gracilis possesses a simple but sophisticated light detecting system, consisting of an eyespot formed by carotenoids globules and a photoreceptor. The photoreceptor of Euglena is characterized by optical bistability, with two stable states. In order to provide important and discriminating information on the series of structural changes that Euglena photoreceptive protein(s) undergoes inside the photoreceptor in response to light, we measured the in vivo absorption spectra of the two stable states A and B of photoreceptor photocycle. Data were collected using two different devices, i.e. a microspectrophotometer and a digital microscope. Our results show that the photocycle and the absorption spectra of the photoreceptor possess strong spectroscopic similarities with a rhodopsin-like protein. Moreover, the analysis of the absorption spectra of the two stable states of the photoreceptor and the absorption spectrum of the eyespot suggests an intriguing hypothesis for the orientation of microalgae toward light.

show abstract

“…This crystal is made up of a single protein and can be interpreted as a three‐dimensional crystal of type I [5], i.e. a stack of two‐dimensional crystal protein layers characterized by in‐plane hydrophobic interactions and held together by hydrophilic interactions as confirmed on the basis of cryo‐fractured images [6].…”

Section: Introductionmentioning

confidence: 99%

“…Other examples of naturally occurring crystalline light‐detecting organelles are the bacteriorhodopsin of Halobacterium halobium , the reaction centers of photosystem II in the photosynthetic membranes of green plants, and the photosynthetic membranes of Rhodopseudomonas viridis and related purple bacteria [7]. Among these, the photoreceptor of Euglena acquires a special meaning since it is the only crystal of a photodetecting protein consisting of about 100 layers [6]. Moreover, Barsanti et al [8] reported the presence of a photochromic pigment in the photoreceptor of Euglena gracilis , which undergoes repeated and reversible fluorescence changes with a determinate kinetics.…”

Section: Introductionmentioning

confidence: 99%

The photoreceptor protein of Euglena gracilis

et al. 2000

Self Cite

View full text Add to dashboard Cite

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

show abstract

Rhodopsin: A Photopigment for Phototaxis in Euglena gracilis

Cited by 16 publications

References 28 publications

Photomovement in Euglena

Photomovement in Euglena

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

The photoreceptor protein of Euglena gracilis

Contact Info

Product

Resources

About