PRESUMED PHOTORECEPTOR PROTEIN AND ULTRASTRUCI'URE OF THE PHOTORECEPTOR ORGANELLE IN THE CILIATED PROTOZOAN, <i>Blepharisma</i>

Matsuoka, Takeshi; Tsuda, Takenori; Ishida, Masaki; Kato, Yoji; Takayanagi, Miyuki; Fujino, Takeshi; Mizuta, Shumpei

doi:10.1111/j.1751-1097.1994.tb05155.x

Cited by 24 publications

(14 citation statements)

References 40 publications

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“…As BP molecules in the granule are quite closely packed (29), it is reasonable to conceive that in vivc they can also be tightly associated with possible electron acceptors. In such a case, an efficient photoinduced electron transfer can occur even if the acceptor molecules have more negative reduction potentials.…”

Section: Discussionmentioning

confidence: 99%

Electron Transfer Fluorescence Quenching of Blepharisma japonicum Photoreceptor Pigments

Angelini

Quaranta

Checcucci

et al. 1998

Photochem & Photobiology

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Abstract— The hypericin analogs blepharismin (BP), oxyblepharismin (OxyBP) and stentorin (ST), the photosensing chromophores responsible for photomotile reactions in the ciliates Blepharisma japonicum (red and blue cells) and Stentor coeruleus, represent a new class of photoreceptor pigments whose chemical structures have recently been determined. In the case of ST it has been shown that the first excited singlet state can be deactivated by donation of an electron to an appropriate acceptor molecule (e.g. a quinone molecule). This charge transfer can be considered a possible mechanism for the primary photoprocess for the photomotile responses in S. coeruleus. To determine whether an electron transfer process also occurs in the deactivation of excited blepharismin, we studied the fluorescence quenching of OxyBP in dimethyl‐sulfoxide (DMSO) and in ethanol using electron acceptors with different reduction potentials. Under our experimental conditions ground state and excited state complexes (like fluorescent exciplexes) are not formed between the fluorophore and the quenchers. In DMSO the bimolecular quenching constant values (kq) calculated on the basis of the best fitting procedures clearly show that the quenching efficiency decreases with the quencher negative reduction potential, E0. The kq (M‐1 s‐1) and E0 (V) values are, respectively, 7.8 times 109 and ‐0.134 for 1,4‐benzoquinone, 8.9 times 109 and ‐0.309 for 1,4‐naphthoquinone, 2.4 times 109 and ‐0.8 for nitrobenzene, 0.009 times 109 and ‐1.022 for azobenzene and 0 and ‐1.448 for benzophenone. These findings point to the conclusion that upon formation of the encounter complex between OxyBP and the quencher, an electron is released from excited OxyBP to the quencher, similar to what happens in ST. It is suggested that in the pigment granules such a light‐induced charge transfer from excited blepharismin to a suitable electron acceptor triggers sensory transduction processes in B. japonicum.

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Section: Discussionmentioning

confidence: 99%

Electron Transfer Fluorescence Quenching of Blepharisma japonicum Photoreceptor Pigments

Angelini

Quaranta

Checcucci

et al. 1998

Photochem & Photobiology

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“…The free‐swimming protozoan, Blepharisma japonicum , has numerous pigment granules containing quinone pigments [1], called blepharismins (Fig. 1 ) [2]; these granules are located just beneath the plasma membrane [3,4]. The pigments are considered to function as photoreceptors modulating the photobehavior of the cell [5,6].…”

Section: Introductionmentioning

confidence: 99%

Blepharismins, produced by the protozoan, Blepharisma japonicum, form ion‐permeable channels in planar lipid bilayer membranes

et al. 2001

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Blepharismins are polycyclic quinones found in the pigment granules of the ciliated protozoan, Blepharisma. Exposure to purified blepharismins results in lethal damage to several other ciliates. We here report that, at cytotoxic concentrations, blepharismins formed cation-selective channels in planar phospholipid bilayer membranes. The channels formed in a diphytanoylphosphatidylcholine bilayer had a K + /Cl 3 permeability ratio of 6.6:1. Single channel recordings revealed the conductance to be quite heterogeneous, ranging from 0.2 to 2.8 nS in solutions containing 0.1 M KCl, possibly reflecting different states of aggregation of blepharismin. Our observations suggest that channel formation is a cytotoxic mechanism of blepharismin's action against predatory protozoa. ß

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“…The complete molecular structure has been determined in the case of blepharismin (for both red and blue form) (Checcucci et al, 1997;Maeda et al, 1997) and stentorin (Spitzner et al, 1998), while it is still unknown in the case of fabrein (Marangoni et al, 1996). In all cases the photoreceptor pigment was described as confined in pigment granules located below the plasma membrane (Marangoni et al, 1996;Matsuoka et al, 1994;Song, 1981) and it was thought that light stimulation caused a proton release in the cytoplasm, which, in an unknown way, could finally alter the membrane potential and cause modifications of the ciliary beating. Moreover, it was suggested that at least in B. japonicum there could have been a different distribution of the pigments along the cell body .…”

Section: Introductionmentioning

confidence: 98%

Evidence for ciliary pigment localization in colored ciliates and implications for their photosensory transduction chain: A confocal microscopy study

Colombetti¹,

Checcucci²,

Lucia³

et al. 2007

Microscopy Res & Technique

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In this study we report for the first time the localization of a photoreceptor pigment in the cilia of the colored heterotrich ciliates Blepharisma japonicum red and blue form, Fabrea salina, and Stentor coeruleus, as result of a confocal microscopy investigation. Optical sectioning confocal microscopy has been used for studying the spatial distribution of the pigment in the cell body, surprisingly showing that, besides its expected presence in the cortical region immediately below the cell membrane, it is located in the cilia too. In order to ascertain possible differences in the pigment fluorescence properties along the cell body, we have measured emission spectra from different parts of it (anterior, posterior, and cilia). Our results clearly indicate that in all cases the spectra are the same, within experimental errors. Finally, we have evaluated the pigment relative fluorescence efficiency of these ciliates. In an ordered scale from lower to greater efficiency, we have S. coeruleus, B. japonicum blue, B. japonicum red, and F. salina. The possible implications of our findings for the process of photosensory transduction are discussed.

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PRESUMED PHOTORECEPTOR PROTEIN AND ULTRASTRUCI'URE OF THE PHOTORECEPTOR ORGANELLE IN THE CILIATED PROTOZOAN, Blepharisma

Cited by 24 publications

References 40 publications

Electron Transfer Fluorescence Quenching of Blepharisma japonicum Photoreceptor Pigments

Electron Transfer Fluorescence Quenching of Blepharisma japonicum Photoreceptor Pigments

Blepharismins, produced by the protozoan, Blepharisma japonicum, form ion‐permeable channels in planar lipid bilayer membranes

Evidence for ciliary pigment localization in colored ciliates and implications for their photosensory transduction chain: A confocal microscopy study

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