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Stentorin, the photosensor molecule and signal transduction in ciliate Stentor coeruleus
Abstract
Stentor coeruleus, a light-green ciliate, is able to detect light with high efficiency and to display a characteristic photophobic response. Stentorin is the photosensor molecule responsible for the light-avoiding behavior in Stentor coeruleus. However, the chemical nature of stentorin and its role in signal transduction, despite having been under intensive investigation, remains poorly understood. In the current study, for the first time, stentorin has been purified, and its structure determined by means of chemical and analytical spectroscopic techniques. Stentorin was found to be 2,2$\sp\prime$,4,4$\sp\prime$,5,5$\sp \prime$,7,7$\sp\prime$-octahydroxy-3,3$\sp\prime $-diisopropylnaphthodianthrone or 2,2$\sp\prime$,4,4$\sp\prime$,5,5$\sp\prime $,7,7$\sp\prime$-octahydroxy-3,6$ \sp\prime$-diisopropylnaphthodianthrone. Stentorin I and stentorin II, two distinct forms of stentorin pigments which can be obtained from Stentor coeruleus cell extract and are separable by gel filtration or hydroxyapatite chromatography, were believed to be glycoproteins. However, a lectin binding study using Concanavalin A (Con A), wheat germ agglutinin (WGA), pea lectin, and a DIG Glycan Differentiation kit (Boehringer Mannheim), suggests that neither stentorin I nor stentorin II are typical glycoproteins. Furthermore, evidence is provided that stentorin I, previously identified as a chromoprotein, is probably a chromophore-detergent complex. The ultimate reaction of Stentor coeruleus to light is ciliary reversal, which is controlled by the bioelectrical properties of the membrane. Our electrophysiological investigation indicates that the membrane potential changes induced by light correlate well with the cell motile responses. The latency for the action potential and that for the stop reaction are shorter, while the duration of the membrane depolarization and that of backward swimming are longer with increasing light intensity.
Subject Area
Biochemistry|Analytical chemistry|Biophysics
Recommended Citation
Tao, Nengbing, "Stentorin, the photosensor molecule and signal transduction in ciliate Stentor coeruleus" (1994). ETD collection for University of Nebraska-Lincoln. AAI9504148.
https://digitalcommons.unl.edu/dissertations/AAI9504148