Target Analysis of Primary Photoprocesses Involved in the Oxyblepharismin-Binding Protein

Plaza, Pascal; Mahet, Mathilde; Martin, Monique M.; Checcucci, Giovanni; Lenci, Francesco

doi:10.1021/jp0642591

Cited by 13 publications

(20 citation statements)

References 47 publications

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“…Photoexcited OxyBP in DMSO was found to decay in about 1 ns and form the triplet state with a yield of 25%. 27 The OxyBP:HSA complex displays a similar behaviour with an excitedstate lifetime of 945 ps and a triplet yield of 65%. 27 The fate of the OxyBP:BAC complex is apparently different.…”

Section: Transient Absorption Spectroscopy Of the Oxybp:bac Complexmentioning

confidence: 88%

“…27 The OxyBP:HSA complex displays a similar behaviour with an excitedstate lifetime of 945 ps and a triplet yield of 65%. 27 The fate of the OxyBP:BAC complex is apparently different. No signature of the triplet state (loss of the stimulated-emission structures and broad positive band peaking around 640 nm 26 ) is detected at long times in the present difference spectra.…”

Section: Transient Absorption Spectroscopy Of the Oxybp:bac Complexmentioning

confidence: 88%

“…Such an interaction is indeed supposed to be at work when oxyblepharismin is bound to its native protein partner (the oxyblepharismin-binding protein, OBIP) in lightadapted B. japonicum. [24][25][26][27] We also used partial denaturation of alpha-crystallin (molten globule state 28 ) as a mean to alter the environment of the chromophore bound to alpha-crystallin. Our objective was to probe the excited-state dynamics of OxyBP in interaction with this modified surrounding and compare it to the case of native alpha-crystallin, in order to bring further evidence that the photophysics of the chromophore is controlled by its interaction with the environment.…”

Section: Introductionmentioning

confidence: 99%

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Steady-state and femtosecond photoinduced processes of blepharismins bound to alpha-crystallin

Youssef¹,

Brazard²,

Ley³

et al. 2008

Photochem Photobiol Sci

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The interaction of blepharismin (BP) and oxyblepharismin (OxyBP) with bovine alpha-crystallin (BAC) has been studied both by steady-state and femtosecond spectroscopy, with the aim of assessing the possible phototoxicity of these compounds toward the eye tissues. We showed that these pigments form with BAC potentially harmful ground-state complexes, the dissociation constants of which have been estimated to be 6 +/- 2 micromol L(-1) for OxyBP and 9 +/- 4 micromol L(-1) for BP. Irradiation with steady-state visible light of solutions of blepharismins in the presence of BAC proved to induce a quenching of both the pigment and the intrinsic protein fluorescences. These effects were tentatively rationalized in terms of structural changes of alpha-crystallin. On the other hand, femtosecond transient absorption spectroscopy was used to check the occurrence of any type I photoactivity of oxyblepharismin bound to alpha-crystallin. The existence of a particular type of fast photoinduced reaction, not observed in former studies with human serum albumin but present in the natural oxyblepharismin-binding protein, could here be evidenced but no specific reaction was observed during the first few nanoseconds after excitation. Partial denaturation of alpha-crystallin was however found to alter the excited-state behaviour of its complex with oxyblepharismin, making it partly resemble that of free oxyblepharismin in solution.

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Section: Transient Absorption Spectroscopy Of the Oxybp:bac Complexmentioning

confidence: 88%

Section: Transient Absorption Spectroscopy Of the Oxybp:bac Complexmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

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Steady-state and femtosecond photoinduced processes of blepharismins bound to alpha-crystallin

Youssef¹,

Brazard²,

Ley³

et al. 2008

Photochem Photobiol Sci

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“…Each granule contains the hipericin-like pigment blepharismin, which is thought to function as the primary photoreceptor eliciting the cell photoresponses (Tao et al, 1994;Song, 1997;Maeda et al, 1997;Matsuoka et al, 1997;Matsuoka et al, 2000). Recent analysis of primary photoprocesses in Blepharisma has revealed, however, that blepharismin undergoes an initial photocycle in the picosecond regime, indicating that the chromophore reaction in these cells does not play any active role in the phototransduction chain (Plaza et al, 2005;Plaza et al, 2007). The possibility that another class of photoreceptors may be utilized by Blepharisma in its photophobic behavior results also from our preliminary investigations, which showed the presence of a presumed rhodopsin-related protein in the cell membrane (H.F., unpublished data), as has been reported for other ciliates (Podesta et al, 1994;Nakaoka et al, 1991;Shinozawa et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

Phosducin interacts with the G-protein βγ-dimer of ciliate protozoanBlepharisma japonicumupon illumination

Sobierajska

Fabczak

2007

Journal of Experimental Biology

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SUMMARY Immunological techniques and high-resolution FRET analysis were employed to investigate the in vivo colocalization and interaction of phosducin(Pdc) with the βγ-subunits of G-protein (Gβγ) in the ciliate Blepharisma japonicum. Immunological techniques revealed that illumination of cells resulted in a decrease in phosphorylation levels of Pdc and its colocalization with Gβγ. The observed light-induced Pdc dephosphorylation was also accompanied by significant enhancement of Gβγ binding by this molecule. Possible formation of the Pdc–Gβγ complex in cells exposed to light was corroborated by FRET between these proteins. Treatment of cells with okadaic acid, an inhibitor of phosphatase activity, entirely prevented Pdc dephosphorylation by light, colocalization of this phosphoprotein with Gβγ and generation of the Pdc–Gβγ complex. Cell fractionation and immunoblotting revealed that in cells exposed to light, the formation of Pdc–Gβγ complex and its translocation into the cytoplasm occur simultaneously with a change in the gel migration of Gβ. Moreover, a 33 kDa immunoanalog of 14-3-3 protein was identified and we showed that this protein is bound by phosphorylated Pdc in a cell adapted to darkness. The results of this study provide additional detailed characterization of the functional properties of the ciliate Pdc. The likely functional role of Pdc in Blepharisma is discussed.

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“…Blepharismin Plaza and coworkers (136,137) have recently extended studies of these naturally occurring chromoprotein complexes to oxyblepharismin (Fig. 1) and its chromoprotein, the oxyblepharismin‐binding protein, which are obtained from light‐adapted cells of B. japonicum.…”

mentioning

confidence: 99%

Photophysics and Multifunctionality of Hypericin‐Like Pigments in Heterotrich Ciliates: A Phylogenetic Perspective

Lobban

Hallam

Mukherjee

et al. 2007

Photochem & Photobiology

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In this paper, we review the literature and present some new data to examine the occurrence and photophysics of the diverse hypericin-like chromophores in heterotrichs, the photoresponses of the cells, the various roles of the pigments and the taxa that might be studied to advance our understanding of these pigments. Hypericin-like chromophores are known chemically and spectrally so far only from the stentorids and Fabrea, the latter now seen to be sister to stentorids in the phylogenetic tree. For three hypericin-like pigments, the structures are known but these probably do not account for all the colors seen in stentorids. At least eight physiological groups of Stentor exist depending on pigment color and presence ⁄ absence of zoochlorellae, and some species can be bleached, leading to many opportunities for comparison of pigment chemistry and cell behavior. Several different responses to light are exhibited among heterotrichs, sometimes by the same cell; in particular, cells with algal symbionts are photophilic in contrast to the well-studied sciaphilous (shadeloving) species. Hypericin-like pigments are involved in some well-known photophobic reactions but other pigments (rhodopsin and flavins) are also involved in photoresponses in heterotrichs and other protists. The best characterized role of hypericin-like pigments in heterotrichs is in photoresponses and they have at least twice evolved a role as photoreceptors. However, hypericin and hypericin-like pigments in diverse organisms more commonly serve as predator defense and the pigments are multifunctional in heterotrichs. A direct role for the pigments in UV protection is possible but evidence is equivocal. New observations are presented on a folliculinid from deep water, including physical characterization of its hypericin-like pigment and its phylogenetic position based on SSU rRNA sequences. The photophysics of hypericin and hypericin-like pigments is reviewed. Particular attention is given to how their excited-state properties are modified by the environment. Dramatic changes in excited-state behavior are observed as hypericin is moved from the homogeneous environment of organic solvents to the much more structured surroundings provided by the complexes it forms with proteins. Among these complexes, it is useful to consider the differences between environments where hypericin is not found naturally and those where it is, notably, for example, in heterotrichs. It is clear that interaction with a protein modifies the photophysics of hypericin and understanding the molecular basis of this interaction is one of the outstanding problems in elucidating the function of hypericin and hypericin-like chromophores.

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Target Analysis of Primary Photoprocesses Involved in the Oxyblepharismin-Binding Protein

Cited by 13 publications

References 47 publications

Steady-state and femtosecond photoinduced processes of blepharismins bound to alpha-crystallin

Steady-state and femtosecond photoinduced processes of blepharismins bound to alpha-crystallin

Phosducin interacts with the G-protein βγ-dimer of ciliate protozoanBlepharisma japonicumupon illumination

Photophysics and Multifunctionality of Hypericin‐Like Pigments in Heterotrich Ciliates: A Phylogenetic Perspective

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